CN113534007A - Lightning arrester leakage current monitoring method and system - Google Patents
Lightning arrester leakage current monitoring method and system Download PDFInfo
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Abstract
The embodiment of the invention discloses a method and a system for monitoring leakage current of an arrester, wherein the method comprises the following steps: acquiring interphase interference current and leakage total current of the lightning arrester; the leakage full current comprises current between the lightning arrester and the ground; removing the inter-phase interference current from the leakage total current to obtain leakage current; acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current; and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle. According to the method, the interphase interference current in the lightning arrester live test is obtained, the leakage current of the lightning arrester is compensated, the interference component passing through the interphase coupling capacitor in the leakage current is eliminated, and the leakage current flowing through the lightning arrester body is reduced. The method improves the accuracy of the lightning arrester live test phase comparison method, is beneficial to testers to accurately sense the equipment state, and improves the safety level of the power system.
Description
Technical Field
The embodiment of the invention relates to a lightning arrester leakage current measuring technology, in particular to a lightning arrester leakage current monitoring method and a lightning arrester leakage current monitoring system.
Background
A zinc oxide arrester (MOA) is a device for protecting electric power equipment, and the current flowing through the arrester is very small at a normal voltage due to the nonlinear characteristic of the resistance of the zinc oxide arrester. And the resistance of the zinc oxide arrester is rapidly reduced under overvoltage, energy is rapidly released, and the function of protecting power equipment is achieved. The zinc oxide arrester has simple structure, small volume and strong current capacity, and is widely applied to power systems.
The zinc oxide arrester can appear ageing in service, the condition such as weing leads to leakage current increase, the arrester generates heat, serious meeting is exploded. Therefore, the operational state of the zinc oxide arrester must be monitored. At present, the state of the lightning arrester is monitored mainly by checking leakage current of a milliammeter arranged below the lightning arrester and judging the state of the lightning arrester according to the size of the leakage current. The leakage current in fact consists of resistive current flowing through the equivalent resistance of the arrester and capacitive current flowing through the equivalent capacitance of the arrester. Under normal voltage, the resistive current is very small, usually less than 10% of the leakage current, and the resistive current reflects the state of the arrester. Therefore, the measurement of the resistive current of the lightning arrester is the key to monitor the state of the lightning arrester.
Disclosure of Invention
The invention provides a method and a system for monitoring leakage current of an arrester, which are used for compensating the leakage total current of the arrester by measuring interphase coupling capacitance interference current and realizing accurate measurement of resistive leakage current and capacitive leakage current of the live test of the arrester.
In a first aspect, an embodiment of the present invention provides a method for monitoring a leakage current of an arrester, where the method includes:
acquiring interphase interference current and leakage total current of the lightning arrester; the leakage full current comprises current between the lightning arrester and the ground;
removing the inter-phase interference current from the leakage total current to obtain leakage current;
acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current;
and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle.
Optionally, the obtaining the inter-phase interference current comprises:
and acquiring the inter-phase interference current detected by an interference current measuring device arranged near the base of the lightning arrester.
Optionally, acquiring a leakage total current of the lightning arrester, including;
and leading out current through a wire clamp fixed on the lightning arrester base to obtain the leakage total current.
Optionally, removing the inter-phase interference current from the full leakage current to obtain a leakage current, including:
discretizing the leakage full current and the interphase interference current to obtain a leakage full current sequence and an interphase interference current sequence, and subtracting the interphase interference current sequence from the leakage full current sequence to obtain a leakage current sequence;
obtaining the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current, wherein the method comprises the following steps:
discretizing the voltage to obtain a voltage sequence;
and detecting zero crossing points of the leakage current sequence and the voltage sequence according to a zero crossing detection method, and solving a phase angle based on the deviation of the zero crossing points of the leakage current sequence and the voltage sequence.
Further, discretizing the leakage full current and the inter-phase interference current to obtain a leakage full current sequence and an inter-phase interference current sequence, including:
and synchronously sampling the signal of the leakage full current acquisition channel and the signal of the interphase interference current acquisition channel by using a clock synchronization signal, and converting the signals into digital signals to obtain a leakage full current sequence and an interphase interference current sequence.
Optionally, at least one of the resistive leakage current and the capacitive leakage current is calculated by the following formula:
wherein, IxIn order to allow a current to leak out,
is the phase angle of voltage and leakage current, IrFor resistive leakage current, IcIs a capacitive leakage current.
In a second aspect, an embodiment of the present invention further provides a lightning arrester leakage current monitoring system, where the system includes:
interference current measuring means for detecting an inter-phase interference current;
the leakage total current measuring device is used for detecting the leakage total current of the lightning arrester;
the voltage measuring device is used for detecting the phase voltage of the lightning arrester;
the measuring device is used for acquiring interphase interference current and leakage total current of the lightning arrester; the leakage full current comprises current between the lightning arrester and the ground;
removing the inter-phase interference current from the leakage total current to obtain leakage current;
acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current;
and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle.
Optionally, the interference current measuring device includes:
an electrical conductor disposed proximate to a base of the arrester; the conductor comprises a metal ball or a metal substrate;
and the output end of the current transformer is connected with the measuring device.
Optionally, the leakage total current measuring device includes a wire clamp, and the wire clamp is fixed to the lightning arrester base and connected to the measuring device.
Optionally, the voltage measuring device is configured to collect a voltage at a primary side or a secondary side of a voltage transformer of a phase line corresponding to the arrester, and wirelessly transmit the voltage to the measuring device.
The embodiment of the invention obtains the interphase interference current and the leakage total current of the lightning arrester; the leakage full current comprises the current between the lightning arrester and the ground; removing interphase interference current from the leakage total current to obtain leakage current; acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current; and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle. The method eliminates the interference component passing through the interphase coupling capacitor in the leakage total current, and reduces the leakage current flowing through the lightning arrester body. The method improves the accuracy of the lightning arrester live test phase comparison method, is beneficial to testers to accurately sense the equipment state, and improves the safety level of the power system.
Drawings
FIG. 1 is an equivalent model of a zinc oxide arrester;
FIG. 2 is an equivalent circuit diagram of interphase interference of the lightning arrester;
FIG. 3 is a vector diagram of interphase interference of an arrester;
FIG. 4 is a vector diagram of interference between phases of another lightning arrester;
fig. 5 is a flowchart of a method for monitoring leakage current of an arrester according to an embodiment of the present invention;
fig. 6 is a flowchart of a method for monitoring leakage current of an arrester according to a second embodiment of the present invention;
fig. 7 is an equivalent circuit diagram of an interference current measurement model according to a second embodiment of the present invention;
fig. 8 is a schematic structural diagram of a leakage current monitoring system for an arrester according to a third embodiment of the present invention;
fig. 9 is a schematic diagram of an interference current measuring apparatus according to a third embodiment of the present invention;
fig. 10 is a deployment diagram of an arrester live-line test field provided by the third embodiment of the invention;
fig. 11 is a flowchart of the operation of the measuring apparatus according to the third embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
At present, the resistive current of the zinc oxide arrester is mainly calculated by a third harmonic method and a phase comparison method, wherein the third harmonic method is based on the quantity relationship between the fundamental wave of the resistive current and the third harmonic wave proposed by the DL/T987-2005 standard, and the third harmonic wave shape is obtained through filtering, so that the resistive current is obtained. The advantage of this approach is that no voltage reference signal is required, but at the same time the limitations are also significant. Firstly, each arrester has a difference, and it cannot be guaranteed that a fixed quantitative relation exists between resistive current fundamental waves and third harmonics. Secondly, the harmonic content of the power grid can also have a serious influence on the method. Under the background of increasingly serious harmonic pollution, the third harmonic of the power grid can seriously interfere with the precision of the method.
Most of the current methods applied in practical production are phase comparison methods, and the principle of the phase comparison method is as follows: the zinc oxide arrester in normal operation can be equivalent to a parallel model of a nonlinear resistor and a capacitor, as shown in fig. 1. However, this method is susceptible to interference from the electric field between the phases, resulting in measurement errors.The electric field interference refers to interphase interference, and an equivalent circuit diagram of the arrester interphase interference is shown in fig. 2. Wherein R isAAnd CAIs the equivalent resistance and capacitance, R, of an A-phase arresterBAnd CBEquivalent resistance and capacitance of B-phase lightning arrester, RCAnd CCEquivalent resistance and capacitance of the C-phase lightning arrester; cab、Cba、Cbc、CcbThe space equivalent capacitance of the adjacent phase grounding terminal is corresponding to the high-voltage terminal of each phase.
Lightning arresters in a transformer substation are often arranged in a straight line, and leakage current of each phase of lightning arrester also comprises adjacent phase interference current flowing through an interphase coupling capacitor besides current flowing through a valve plate of the lightning arrester. Taking phase B as an example, the total leakage current IB＝Ib+Iab’+Icb’In which IbFor the current flowing through the arrester valve plate, Iab’A phase passes through an air coupling capacitor CabCurrent to B phase, Icb’The C phase passes through an air coupling capacitor CcbCurrent flowing to the B phase. I isb’For the current flowing through the equivalent capacitance of the arrester valve plate, IBrIs the current flowing through the equivalent resistance of the lightning arrester valve plate. When C is presentab＝Ccb＝Cba＝CbcWhen, as shown in FIG. 3, Iab’And Icb’Of the resultant vector Ib”Direction and B compatible current Ib’The direction is opposite, but the B-phase resistance current is not influenced, so that the amplitude and the angle of the total leakage current are reduced. When C is presentab＝Cba>Cbc＝CbcWhen, as shown in FIG. 4, Iab’And Icb’Of the resultant vector Ib”The direction is shifted clockwise atBrIn a direction producing a component I in the opposite directionBr’The B-phase resistive current is offset, and a negative value of the resistive current appears in severe cases. Due to the existence of interphase interference, the electrified test result of the lightning arrester is distorted, and the equipment state cannot be correctly reflected.
Example one
Fig. 5 is a flowchart of a method for monitoring leakage current of an arrester according to an embodiment of the present invention, where the present embodiment is applicable to measuring a leakage current condition of the arrester, and the method may be executed by an arrester leakage current monitoring system, and the system may be implemented by software and/or hardware. Referring to fig. 5, the monitoring method includes the steps of:
s101, acquiring interphase interference current and leakage total current of a lightning arrester; the leakage full current includes a current between the arrester and the ground.
The inter-phase interference current is a current formed by inter-phase coupling capacitors. For the metal oxide lightning arrester arranged in a straight line, when the leakage current live detection is carried out, the A, C phase current phases are required to be shifted towards the B phase direction due to the influence of inter-phase interference, and generally the shift angle is about 2-4 degrees, so that the A phase resistance leakage current is increased, the C phase change is small or even negative, and the B phase is centered. The phase change is caused by interphase coupling capacitance of the three-phase lightning arrester, so that the phase change occurs when three-phase bottom current and single phase operation are carried out. For example, the interference current measuring device may be used to obtain the inter-phase interference current.
When the arrester is in healthy operation, when not considering interphase interference, the interphase interference model is:
wherein R isaRepresenting equivalent resistance of a phase A lightning arrester valve plate, CaRepresenting equivalent capacitance of a valve plate of the A-phase lightning arrester; rbRepresenting equivalent resistance of valve plate of B-phase lightning arrester, CbRepresenting equivalent capacitance of a valve plate of the B-phase lightning arrester; rcRepresenting the equivalent resistance of the valve plate of the C-phase lightning arrester, CcRepresenting the equivalent capacitance of the valve plate of the C-phase lightning arrester; . However, in practice, a lightning arrester operating at a power generation site cannot avoid interference from inter-phase coupling capacitance. When inter-phase interference is considered, the above equation may be changed to:
wherein, CA＝Ca+Ca0，Ca0Equivalent capacitance for coupling phase A with ground through air; cB＝Cb+Cb0，Cb0Equivalent capacitance for coupling phase A with ground through air; cC＝Cc+Cc0，Cc0Phase a is the equivalent capacitance coupling through air to ground. Compared with the formula (1), the leakage current of the formula (2) has more interference components, and as can be seen from the above analysis, the interference components affect the solution of the current, so that the components must be separated.
The current flowing through the zinc oxide resistor disc is called the leakage total current of the zinc oxide arrester. The leakage full current of the arrester includes a current between the arrester and the ground. Through being fixed in the arrester base to the fastener, introduce the electric current that flows through the arrester to electrified test instrument in, realize the measurement to leakage current. The leakage total current of the lightning arrester can reflect the insulation condition of the lightning arrester, and is an important means for judging the quality of the lightning arrester under the operating voltage.
And S102, removing the inter-phase interference current from the leakage total current to obtain leakage current.
The leakage full current is superposed with the inter-phase interference current, so that the leakage current can be obtained only by subtracting the leakage full current and the inter-phase interference current. The leakage current is actually the current that flows through the insulation portion of the arrester without a fault and under the action of an applied voltage. Therefore, the method is one of important marks for measuring the insulation performance of the electric appliance and is a main index for the safety performance of the product.
S103, obtaining the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current.
When the lightning arrester operates under power frequency voltage, the current flowing through the lightning arrester comprises a resistive component and a capacitive component, so that the detection and extraction of the resistive current component are realized, the operating voltage at two ends of the lightning arrester and the total current flowing through the lightning arrester must be synchronously monitored, and the voltage monitoring must have high phase precision. The voltage of the arrester can be detected by a measuring device.
The measuring device may be, for example, a voltage sensor, a voltage transformer. High-precision voltage sensors such as capacitance sensors can be connected in parallel at two ends of the lightning arrester. The voltage transformer is mainly used for supplying power to a measuring instrument and a relay protection device and measuring the voltage, power and electric energy of a line, when the voltage transformer operates, a primary winding N1 is connected on the line in parallel, and a secondary winding N2 is connected with the instrument in parallel. Therefore, when measuring the voltage on the high-voltage line, although the primary voltage is high, the secondary voltage is low, and the safety of operators and instruments can be ensured.
And because the phase difference exists between the voltage waveform and the leakage current waveform, the phase angle can be obtained by calculating the voltage and the leakage current. The compensation of the leakage current is realized, and the accurate calculation of the resistive leakage current is finally realized.
And S104, obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle.
Under the operating voltage, the leakage current flowing through the lightning arrester comprises a resistive leakage current component and a capacitive leakage current component. The resistive leakage current is formed by the fact that the bus voltage reaches a grounding wire through a high-value resistor of a lightning arrester valve plate; the capacitive leakage current is formed by the fact that bus voltage reaches a grounding wire through a capacitor between lightning arrester valve plates; the magnitude of the resistive leakage current is an important parameter determining the performance of the arrester. Calculating the leakage current and the phase angle, multiplying the leakage current by the cosine value of the phase angle to obtain the resistive leakage current, and multiplying the leakage current by the sine value of the phase angle to obtain the capacitive leakage current.
The embodiment of the invention obtains the interphase interference current and the leakage total current of the lightning arrester; the leakage full current comprises the current between the lightning arrester and the ground; removing interphase interference current from the leakage total current to obtain leakage current; acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current; and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle. According to the method, the interference component of the inter-phase coupling capacitor in the leakage total current is eliminated by measuring the inter-phase interference current, the leakage total current of the lightning arrester is compensated, the leakage current flowing through the lightning arrester body is reduced, and accurate measurement of the resistive leakage current and the capacitive leakage current of the lightning arrester in an electrified test is realized.
Example two
In this embodiment, the refining is performed based on the above embodiment, and optionally, the obtaining the inter-phase interference current includes: and acquiring the inter-phase interference current detected by an interference current measuring device arranged near the base of the lightning arrester. Acquiring leakage total current of the lightning arrester, including; and leading out current through a wire clamp fixed on the lightning arrester base to obtain the leakage total current.
Fig. 6 is a flowchart of a method for monitoring leakage current of an arrester according to a second embodiment of the present invention, and with reference to fig. 6, the method includes:
s201, acquiring the inter-phase interference current detected by an interference current measuring device arranged near a base of the lightning arrester.
In the lightning arrester live test, an interference current measuring device is placed beside a lightning arrester base, and the inter-phase interference current passing through the air coupling capacitor can be read according to a measuring result. Fig. 7 is an equivalent circuit diagram of an interference current measurement model in the third embodiment of the present invention. Referring to fig. 7, taking phase B as an example: wherein C isb0An equivalent capacitance of B-phase high-voltage end coupled with the ground through air, CabA capacitor with A phase high voltage end coupled with B phase ground end via air, CcbThe same principle is that the C phase high voltage end and the B phase grounding end are connected through air coupling capacitors. Thus, the current I measured by the current transformerbmComprises the following steps:
Ibmthe component of the phase-B lightning arrester is that the leakage current of air flows from the high-voltage end of the phase-B lightning arrester to the grounding end and the leakage current of air flows from the high-voltage end of the phase-A, C to the grounding end of the phase-B lightning arrester, so that IbmNamely the interference current of the B phase. Similarly, the device is arranged beside the A-phase or C-phase lightning arrester base to measure A-phase interference current IamCurrent interfering with Ccm。
Optionally, S202, the leakage full current is obtained by drawing current through a wire clamp fixed to the lightning arrester base.
Wherein, the leakage total current of the lightning arrester is the current between the lower end of the lightning arrester and the ground. Through being fixed in the arrester base to the fastener, introduce the electric current that flows through the arrester to electrified test instrument in, realize the measurement to leakage current.
S203, removing the inter-phase interference current from the leakage total current to obtain leakage current;
optionally, removing the inter-phase interference current from the full leakage current to obtain a leakage current, including:
discretizing the leakage full current and the interphase interference current to obtain a leakage full current sequence and an interphase interference current sequence, and subtracting the interphase interference current sequence from the leakage full current sequence to obtain a leakage current sequence;
discretizing the leakage full current and the interphase interference current to obtain a leakage full current sequence and an interphase interference current sequence, and performing subtraction operation in a data processor, specifically, correspondingly subtracting the value of the interphase interference current sampling sequence from the value of the leakage full current sampling sequence to obtain a leakage current sequence after the interphase interference current is eliminated, and recording the leakage current sequence as a sequence 1.
And S204, acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current.
The voltage waveform of A, B, C three phases of the lightning arrester is obtained and converted into a discrete digital signal sequence, which is recorded as sequence 2, by using a digital signal processing technology.
And detecting zero crossing points of the leakage current sequence and the voltage sequence according to a zero crossing detection method, and solving a phase angle based on the deviation of the zero crossing points of the leakage current sequence and the voltage sequence.
The purpose of the live test of the lightning arrester is to separate resistive leakage current from leakage total current. However, actually, due to the existence of the inter-phase interference, the inter-phase interference current is superimposed in the leakage total current, and the above method for measuring the interference current of the lightning arrester of each phase is obtained, so that the leakage current can be obtained only by subtracting the interference current from the leakage total current, and the specific formula is as follows:
the leakage current can be measured at the down lead of the lightning arrester, then the zero crossing points of the sequences 1 and 2 are detected according to a zero crossing detection method, and the phase difference, namely the phase angle, between the voltage waveform and the leakage current waveform is obtained according to the deviation of the zero crossing points. Zero-crossing detection refers to the detection made by the system when a zero is passed as the waveform transitions from a positive half cycle to a negative half cycle in an alternating current system. The leakage detection of the leakage switch is to detect zero sequence current.
For example, the signal of the leakage full current acquisition channel and the signal of the inter-phase interference current acquisition channel may be synchronously sampled by using a clock synchronization signal, and converted into a digital signal to obtain a leakage full current sequence and an inter-phase interference current sequence.
The circuit for converting an Analog signal into a Digital signal is called an Analog-to-Digital Converter (a/D Converter for short), and the a/D conversion is used to convert an Analog signal with continuous time and continuous amplitude into a Digital signal with discrete time and discrete amplitude, so the a/D conversion generally includes 4 processes of sampling, holding, quantizing and encoding. The basic principle of such a converter is to sample the incoming analog signal at regular time intervals and compare it with a series of standard digital signals, which converge successively until the two signals are equal. And the leakage total current and the interphase interference current pass through the analog-to-digital converter, and the two channel signals are synchronously sampled by using a clock synchronization signal. After the current is converted into a digital signal, a leakage full current sequence and an interphase interference current sequence can be obtained.
Optionally, at least one of the resistive leakage current and the capacitive leakage current is calculated by the following formula:
wherein, IxFor leakage current, phi is the phase angle between voltage and leakage current, IrFor resistive leakage current, IcIs a capacitive leakage current.
As can be seen from the above formula, the sine component of the leakage current is resistive leakage current, and the cosine component of the leakage current is capacitive leakage current. The leakage total current of the arrester contains resistive leakage current (active component) and capacitive leakage current (reactive component). Under the normal operation condition, the main current flowing through the lightning arrester is capacitive leakage current, and the resistive leakage current only accounts for a very small part, about 10% -20%.
The embodiment of the invention obtains the interphase interference current, compensates the leakage total current of the lightning arrester and obtains the leakage current for eliminating the interphase interference current. Discretizing the leakage total current and the interphase interference current to obtain a leakage total current sequence and an interphase interference current sequence, and subtracting the two sequences to obtain a leakage current sequence; discretizing the voltage to obtain a voltage sequence; and detecting zero crossing points of the leakage current sequence and the voltage sequence according to a zero crossing detection method, and solving a phase angle based on the deviation of the zero crossing points of the leakage current sequence and the voltage sequence. And the resistive leakage current and the capacitive leakage current are obtained through formula calculation, so that the lightning arrester live test can be accurately measured.
EXAMPLE III
Fig. 8 is a schematic structural diagram of a leakage current monitoring system for an arrester according to a third embodiment of the present invention; fig. 9 is a schematic diagram of an interference current measuring apparatus according to a third embodiment of the present invention; fig. 10 is a deployment diagram of an arrester live-line test field provided by the third embodiment of the invention; fig. 11 is a flowchart of the operation of the measuring apparatus according to the third embodiment of the present invention. In this embodiment, corresponding to the above method embodiment, referring to fig. 8, the monitoring system 200 includes: disturbance current measuring means 201, leakage total current measuring means 202, voltage measuring means 203 and measuring means 204.
The interference current measuring device 201 is used for detecting an inter-phase interference current; the leakage total current measuring device 202 is used for detecting the leakage total current of the lightning arrester; the voltage measuring device 203 is used for detecting the phase voltage of the lightning arrester; the measuring device 204 is used for acquiring inter-phase interference current and leakage total current of the lightning arrester; the leakage full current comprises current between the lightning arrester and the ground; removing the inter-phase interference current from the leakage total current to obtain leakage current; acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current; and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle.
The embodiment of the invention arranges an interference current measuring device, a leakage total current measuring device, a voltage measuring device and a measuring device. The device eliminates interference components passing through the interphase coupling capacitor in the leakage total current, reduces the leakage current flowing through the arrester body, improves the accuracy of the lightning arrester live-line test phase comparison method, is beneficial to testers to accurately sense the equipment state, and improves the safety level of the power system.
Optionally, the interference current measuring device comprises:
an electrical conductor disposed proximate to a base of the arrester; the electrical conductor comprises a metal ball or a metal substrate.
And the output end of the current transformer is connected with the measuring device.
Optionally, the leakage total current measuring device comprises a wire clamp fixed to the arrester base and connected to the measuring device.
Referring to fig. 9, the conductive body 301 includes a metal ball or a metal substrate, and the conductive body 301 is exemplified by a metal ball in fig. 9. The conductor 301 is disposed near the base of the arrester, and the lower end thereof is connected to the insulating rod 302. The metal ball or the metal substrate has no requirement on the shape and can be made of metal and other materials with better conductive performance. The first end of the current transformer 303 is connected with the metal ball, the second end is connected with the grounding lead 304, and the output end of the current transformer 303 is connected with the measuring device.
The current transformer is a miniature current transformer, and is generally used in various electric power instruments for measurement and protection. Compared with the common transformer, the miniature transformer has the characteristics of smaller volume, higher precision and the like. The miniature voltage transformer is a current type voltage transformer, and a primary resistor and a secondary resistor are connected in series in a circuit. The voltage is converted into current, and after the current is converted by the mutual inductor, the primary output current signal is converted into the required voltage by the sampling resistor.
The leakage full current refers to the current between the lower end of the lightning arrester and the ground. The wire clamp in the leakage full current measuring device is fixed on the lightning arrester base, and the current flowing through the lightning arrester is introduced into the measuring device, so that the leakage current is measured.
Optionally, the voltage measuring device is configured to collect a voltage at a primary side or a secondary side of a voltage transformer of a phase line corresponding to the arrester, and wirelessly transmit the voltage to the measuring device.
The voltage measuring device is a Potential Transformer (PT) sending device, and the purpose of voltage transformation by the PT is mainly to supply power to a measuring instrument and a relay protection device, and to measure the voltage, power, and electric energy of a line. The measuring device selects the lightning arrester live test equipment, the lightning arrester live test can judge the aging and damping conditions of the lightning arrester valve block by measuring the resistive component in the leakage current of the lightning arrester valve block under the condition of no power failure, and the lightning arrester live test device has the advantage of incomparable power failure measurement. In field test, three paths of signals need to be input into lightning arrester live test equipment, namely a voltage signal of the lightning arrester, a lightning arrester leakage current signal and an interphase interference current signal.
Illustratively, referring to fig. 10, the leakage total current led out from the lightning arrester base and the inter-phase interference current led out from the interference current measuring device are respectively input to the measuring equipment. The voltage transformer transmitting equipment is responsible for collecting A, B, C three-phase primary side voltage or secondary side voltage output waveforms, and converts the three-phase primary side voltage or secondary side voltage output waveforms into a discrete digital signal sequence by using a digital signal processing technology. And transmitting the discrete A, B, C three-phase voltage digital signal sequence to lightning arrester live test equipment in a wireless transmission mode.
Referring to fig. 11, the lightning arrester live test device is composed of a low pass filter circuit, an a/D conversion circuit, and a main control chip circuit. First, in S401: synchronously collecting leakage current and interphase interference current; after synchronously sampling the leakage current and the interference current from the two channels respectively, performing S402 low-pass filtering; firstly, eliminating high-frequency noise interference through a filter circuit; then, in S403: A/D conversion; converting the analog signal into a discrete digital signal through an A/D conversion circuit; proceeding to S404: performing subtraction operation on the signal sequence; the main control chip firstly carries out subtraction operation on the two sections of sampling sequences to obtain leakage current after the interphase interference is eliminated. Then, S405: reading a voltage signal sequence; the voltage signal and voltage transformer sending equipment is responsible for collecting and converting the voltage signal and voltage transformer sending equipment into a discrete digital signal sequence. Next, step S406: acquiring a phase angle; comparing the zero crossing points of the synchronously sampled voltage signal sequence and the leakage current sequence to obtain the included angle between the voltage and the current; finally, S407 is performed: calculating resistive leakage current; the resistive leakage current solving can be completed according to the formula in the method embodiment.
The lightning arrester leakage current monitoring system provided by the embodiment of the invention can execute the method provided by any embodiment of the invention, and has the corresponding functional modules and beneficial effects of executing the lightning arrester leakage current monitoring method. It should be noted that, in the embodiment of the lightning arrester leakage current monitoring system, each included unit and module is only divided according to functional logic, but is not limited to the above division, as long as the corresponding function can be realized; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A method for monitoring leakage current of an arrester is characterized by comprising the following steps:
acquiring interphase interference current and leakage total current of the lightning arrester; the leakage full current comprises current between the lightning arrester and the ground;
removing the inter-phase interference current from the leakage total current to obtain leakage current;
acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current;
and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle.
2. The method of claim 1, wherein obtaining an inter-phase interference current comprises:
and acquiring the inter-phase interference current detected by an interference current measuring device arranged near the base of the lightning arrester.
3. The method according to claim 1, characterized in that the leakage total current of the lightning arrester is obtained, comprising;
and leading out current through a wire clamp fixed on the lightning arrester base to obtain the leakage total current.
4. The method according to claim 1, wherein removing the inter-phase interference current from the full leakage current to obtain a leakage current comprises:
discretizing the leakage full current and the interphase interference current to obtain a leakage full current sequence and an interphase interference current sequence, and subtracting the interphase interference current sequence from the leakage full current sequence to obtain a leakage current sequence;
obtaining the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current, wherein the method comprises the following steps:
discretizing the voltage to obtain a voltage sequence;
and detecting zero crossing points of the leakage current sequence and the voltage sequence according to a zero crossing detection method, and solving a phase angle based on the deviation of the zero crossing points of the leakage current sequence and the voltage sequence.
5. The method according to claim 4, wherein discretizing the leakage full current and the inter-phase interference current to obtain a leakage full current sequence and an inter-phase interference current sequence comprises:
and synchronously sampling the signal of the leakage full current acquisition channel and the signal of the interphase interference current acquisition channel by using a clock synchronization signal, and converting the signals into digital signals to obtain a leakage full current sequence and an interphase interference current sequence.
6. The method of claim 1, wherein at least one of the resistive leakage current and the capacitive leakage current is calculated by the following equation:
wherein, IxIn order to allow a current to leak out,
is the phase angle of voltage and leakage current, IrFor resistive leakage current, IcIs a capacitive leakage current.
7. An arrester leakage current monitoring system, comprising:
interference current measuring means for detecting an inter-phase interference current;
the leakage total current measuring device is used for detecting the leakage total current of the lightning arrester;
the voltage measuring device is used for detecting the phase voltage of the lightning arrester;
the measuring device is used for acquiring interphase interference current and leakage total current of the lightning arrester; the leakage full current comprises current between the lightning arrester and the ground;
removing the inter-phase interference current from the leakage total current to obtain leakage current;
acquiring the voltage of the lightning arrester, and calculating a phase angle according to the voltage and the leakage current;
and obtaining at least one of resistive leakage current and capacitive leakage current according to the leakage current and the phase angle.
8. The system of claim 7, wherein the interference current measuring device comprises:
an electrical conductor disposed proximate to a base of the arrester; the conductor comprises a metal ball or a metal substrate;
and the output end of the current transformer is connected with the measuring device.
9. The system of claim 7, wherein the full current leakage measurement device comprises: and the wire clamp is fixed on the lightning arrester base and is connected with the measuring device.
10. The system according to claim 7, wherein the voltage measuring device is configured to collect the voltage on the primary side or the secondary side of the voltage transformer of the phase line corresponding to the lightning arrester, and wirelessly transmit the voltage to the measuring device.
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Application publication date: 20211022 |