CN115902412A - Detection circuit and method for double-voltage-level direct-current insulation resistance based on dynamic difference method - Google Patents
Detection circuit and method for double-voltage-level direct-current insulation resistance based on dynamic difference method Download PDFInfo
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Abstract
The invention discloses a detection circuit and a detection method for a double-voltage-level direct-current insulation resistor based on a dynamic difference method t1 Second switching bridge resistor R t2 Third switching bridge resistor R t3 Fourth switching bridge resistor R t4 Positive pole change-over switch K 1 Negative pole change-over switch K 2 First switching bridge resistor R t1 And a second switching bridge resistor R t2 One end of (A) is connected in parallel to ground, R t1 And R t2 The other end of the positive electrode passes through a positive electrode change-over switch K 1 Resistance R to ground of bus anode of direct current system of transformer substation + Parallel, third switched bridge resistor R t3 And a fourth switching bridge resistor R t4 One end of (A) is connected in parallel to ground, R t3 And R t4 The other end of the switch is switched to a negative pole through a negative pole switch K 2 Bus cathode ground resistance R of direct current system of transformer substation ‑ And (4) connecting in parallel. The invention can overcome the defect that the traditional insulation detection circuit is only suitable for the bureau of a single-voltage-level direct-current systemThe method is limited and is suitable for transformer substation direct current systems with two voltage levels.
Description
Technical Field
The invention relates to the field of insulation detection of a direct current system of a transformer substation, in particular to a double-voltage-level direct current insulation detection circuit based on a dynamic difference method and a detection method thereof.
Background
The conventional insulation detection methods of the direct current system are more, and the conventional methods comprise an electric bridge method, a variable frequency detection method, a direct current leakage current method and a dynamic difference value method, wherein the electric bridge method can only be used for detecting the insulation of a bus and cannot detect the insulation of a branch circuit; the frequency conversion detection method can increase the voltage ripple coefficient of the system, thereby reducing the resolution; the direct current leakage current method can detect both bus insulation and branch insulation, but the leakage current is usually small, and the zero drift of the direct current sensor may cause false alarm; the dynamic difference method is based on the improvement of a direct current leakage method, and the insulation detection is realized by obtaining the ratio of the voltage variation of a bus and a branch to the leakage current variation after the resistors are switched twice.
However, the current dynamic difference method is only suitable for a substation direct current system with a single voltage level, and the substation direct current system usually has two voltage levels of 110V and 220V, so that the requirement of developing detection on a substation with two direct current voltage levels cannot be met, the universality is poor, and if the instrument selection is incorrect, the problems of large measurement error and insufficient precision can be caused.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides the detection circuit and the detection method of the double-voltage-level direct-current insulation resistance based on the dynamic difference method, so that the detection circuit and the detection method can be suitable for detecting the insulation resistance of the transformer substation with two voltage levels, and overcome the limitation that the traditional direct-current insulation detection circuit can only be suitable for a single-voltage-level direct-current system, thereby improving the universality of the detection circuit.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a detection circuit of a double-voltage-level direct-current insulation resistor based on a dynamic difference method, which is characterized in that the detection circuit is connected into a direct-current system, and a bus insulation resistor of the direct-current system is recorded as a positive ground resistor R + Negative resistance to ground R - (ii) a The insulation resistance of the branch circuit on the I branch circuit of the direct current system to the ground is recorded as R i And the insulation resistance of the branch on the I-branch opposite to the ground is recorded as R i+ On branch No. iThe negative insulation resistance to ground of the branch is recorded as R i- (ii) a The insulation resistance of the branch circuit on the I-1 branch circuit of the direct current system to the ground is recorded as R i-1 And the insulation resistance of the branch on the No. i-1 branch to the ground is recorded as R (i-1)+ And the branch negative earth insulation resistance on the i-1 branch is recorded as R (i-1)- ；
The detection circuit includes: first switching bridge resistor R t1 Second switching bridge resistor R t2 Third switching bridge resistor R t3 Fourth switching bridge resistor R t4 Positive pole change-over switch K 1 Negative pole change-over switch K 2 ；
If the bus insulation resistance in the direct current system is detected, the connection relationship between the detection circuit and the direct current system is as follows:
the resistance R to ground + Is passed through the positive electrode changeover switch K 1 And the first switching bridge resistor R t1 Or the second switching bridge resistance R t2 Is connected in parallel to a ground resistor R + Is connected with the first switching bridge resistor R t1 And the other end of the second switching bridge resistor R t2 The other end of the first and second connecting rods is connected;
by a first switching bridge resistor R t1 And a second switching bridge resistor R t2 Forming a first set of switches;
the positive electrode change-over switch K 1 And the resistance to ground R + One end of the positive pole U is connected into a direct current system + A common terminal;
the negative resistance to ground R - One end of the negative pole is connected with the negative pole change-over switch K 2 And the third switching bridge resistor R t3 Or a fourth switching bridge resistor R t4 Is connected in parallel to one end of the negative resistance to ground R - Is connected with the third switching bridge resistor R t3 And the other end of the fourth switching bridge resistor R t4 The other end of the first and second connecting rods is connected;
by switching the bridge resistance R by the third t3 And a fourth switching bridge resistor R t4 Forming a second group of switches;
the negative electrode change-over switch K 2 And the stationThe negative resistance to ground R - One end of the negative pole U is connected into a direct current system - A common terminal;
if the branch insulation resistance on the I branch in the direct current system is detected, the connection relationship between the detection circuit and the direct current system is as follows:
the insulation resistance of the branch circuit just facing the ground is recorded as R i+ Is passed through the positive electrode changeover switch K 1 And the first switching bridge resistor R t1 Or the second switching bridge resistance R t2 One end of the branch is connected in parallel, and the insulation resistance of the branch opposite to the ground is recorded as R i+ Respectively with the first switching bridge resistor R t1 And the other end of the second switching bridge resistor R t2 The other end of the connecting rod is connected;
by a first switching bridge resistor R t1 And a second switching bridge resistor R t2 Forming a first set of switches;
the positive pole change-over switch K 1 The insulation resistance opposite to the branch circuit to the ground is recorded as R i+ One end of the positive pole U is connected into a direct current system + A common terminal;
the negative ground insulation resistance of the branch is recorded as R i- One end of the negative pole is connected with the negative pole change-over switch K 2 And the third switching bridge resistor R t3 Or a fourth switching bridge resistor R t4 One end of the branch is connected in parallel, and the negative earth insulation resistance of the branch is recorded as R i- Is connected with the third switching bridge resistor R t3 And the other end of the second switching bridge resistor R t4 The other end of the connecting rod is connected;
by switching the bridge resistance R t3 And a fourth switching bridge resistor R t4 Forming a second group of switches;
the negative electrode change-over switch K 2 And the negative earth insulation resistance of the branch circuit is recorded as R i- One end of the negative pole U is connected into a direct current system - A common terminal;
the insulation resistance of the branch circuit just facing the ground is recorded as R i+ The other end of (2) and the branch negative earth insulation resistance are recorded as R i- The other ends of the two are all grounded.
The invention relates to a bus insulation resistance detection method based on a dynamic difference method, which is characterized in that the method is applied to a detection circuit and is carried out according to the following steps:
step a1, judging the voltage level of the direct current system, and if U =220V, executing step a2; if U =110V, executing step a3;
step a2: detecting the bus insulation resistance of a direct current system with the voltage grade of 220V:
step a2.1, closing the positive pole change-over switch K 1 First switch bridge resistor R t1 A resistor R directly opposite to the direct current system + Parallel connection, in which case the DC ground fault finder is used to detect the current flowing through the first switching bridge resistor R t1 Has a current of I a Detecting the first switching bridge resistance R t1 Has a voltage of U at both ends 1+ The voltage at the two ends of the negative-to-ground resistor R-is U 1- Then, there are:
step a2.2, turning off the positive pole change-over switch K 1 Closing the negative pole changeover switch K 2 Switching the third bridge resistor R t3 And a negative resistance to ground R of the direct current system - In parallel connection, the DC ground fault finder is used for detecting the current flowing through the third switching bridge resistor R t3 Has a current of I b Detecting the third switching bridge resistance R t3 Has a voltage of U at both ends 2- Direct resistance to ground R + Has a voltage of U at both ends 2+ Then, there are:
step a2.3, obtaining the right-to-ground resistor R by using the formulas (5) and (6) after the formulas (1) to (4) are combined + And a negative resistance to ground R - ：
Step a3: detecting a bus insulation resistance of a direct current system with the voltage grade of 110V;
step a3.1, closing the positive pole change-over switch K 1 Second switching bridge resistor R t2 A resistor R directly opposite to the direct current system + Parallel connection, at the moment, the direct current ground fault finder is utilized to detect the current flowing through the second switching bridge resistor R t2 Has a current of I a Detecting the second switching bridge resistance R t2 Has a voltage of U at both ends 1+ The voltage at both ends of the negative ground resistor R-is U 1- Then, there are:
step a3.2, disconnecting the positive pole change-over switch K 1 Closing negative pole change-over switch K 2 A fourth switching bridge resistor R t4 And a negative resistance to ground R of the direct current system - Parallel connection, at the moment, the DC ground fault finder is utilized to detect the current flowing through the fourth switching bridge resistor R t4 Has a current of I b Detecting the fourth switching bridge resistance R t4 Has a voltage of U at both ends 2- Just opposite to the ground resistance R + Has a voltage of U at both ends 2+ Then, there are:
step 3.3, obtaining the right-to-ground resistor R by using the formula (9) and the formula (10) after the formula (5) to the formula (8) are combined + And a negative resistance to ground R - ：
The invention relates to a method for detecting a branch ground insulation resistance based on a dynamic difference method, which is characterized by being applied to a detection circuit and carried out according to the following steps:
step b1: judging the voltage level of the direct current system, and if U =220V, executing step b2; if U =110V, executing step b3;
and b2: switch off positive pole change-over switch K 1 Closing the negative pole changeover switch K 2 Switching to R t3 Detecting the voltage U of the positive bus i+ And collecting leakage current delta I of the I branch i1 And has the following components:
closed positive pole change-over switch K 1 Switching to R t1 On/off switch K 2 Detecting the voltage U of the positive bus i ′ + And collecting leakage current delta I of branch I i2 And has the following components:
after the vertical type (11) and the formula (12) are combined, the branch circuit ground insulation resistance R is calculated by using the formula (13) and the formula (14) i ：
Step b3: switch off positive pole change-over switch K 1 Closing negative pole change-over switch K 2 Switching to R t4 Detecting the voltage U of the positive bus i+ And collecting leakage current delta I of the I branch i1 And has the following components:
closed positive pole change-over switch K 1 Switching to R t2 On/off switch K 2 Detecting the voltage U of the positive bus i ′ + And collecting leakage current delta I of the I branch i2 And has the following components:
after the vertical type (11) and the formula (12) are combined, the branch circuit ground insulation resistance R is calculated by using the formula (13) and the formula (14) i ：
Compared with the prior art, the invention has the beneficial effects that:
the invention can provide a detection circuit and a detection method of a double-voltage-level direct-current insulation resistor based on a dynamic difference method aiming at the limitation that the existing insulation resistor detection circuit can only be suitable for a single-voltage-level direct-current system, and the detection is divided into two parts: the detection of the insulation resistance of the bus and the detection of the insulation resistance of the branch to the ground are realized by four switching bridge resistors and two groups of switching switches based on a dynamic difference method aiming at the detection of the two different insulation resistances. The method comprises the steps of selecting corresponding change-over switches according to the actual voltage grade situation on site, and adopting a targeted detection strategy, so as to construct a set of detection circuit integrating a dynamic difference method and a double-voltage-grade direct-current insulation resistor of a double-change-over switch. Through the detection circuit of the double-voltage-level direct-current insulation resistance, an insulation resistance detection device can be applied to double-voltage levels by taking effective measures, so that the universality of the insulation resistance detection circuit is realized, technical breakthroughs are obtained in the direct-current insulation resistance detection technology of China, the technical level of the universality of the direct-current insulation resistance detection of China can be greatly improved, the reliability and the international competitiveness of insulation resistance detection products of China are improved, the modernization level of the electric power detection of China is improved, and huge social and economic benefits are brought to electric power workers and electric power enterprises.
Drawings
FIG. 1 is a schematic diagram of a DC bus switching bridge resistor according to the present invention;
FIG. 2 is a circuit diagram of the equivalent of bus insulation detection of the DC insulation detection circuit of the present invention;
FIG. 3 is a circuit diagram of equivalent branch insulation detection of the DC insulation detection circuit of the present invention.
Detailed Description
In this embodiment, a detection circuit for a dual-voltage-level dc insulation resistor based on a dynamic difference method is connected to a dc system, and a bus insulation resistor of the dc system is recorded as a positive ground resistor R + Negative resistance to ground R - (ii) a The insulation resistance to ground of the branch on branch i of the DC system is recorded asR i And the insulation resistance of the branch on the No. i branch facing the ground is recorded as R i+ And the negative earth insulation resistance of the branch on the I branch is recorded as R i- (ii) a The insulation resistance of the branch circuit on the I-1 branch circuit of the direct current system to the ground is recorded as R i-1 And the insulation resistance of the branch on the No. i-1 branch to the ground is recorded as R (i-1)+ And the negative earth insulation resistance of the branch on the I-1 branch is recorded as R (i-1)-
As shown in fig. 1, the detection circuit includes: first switching bridge resistor R t1 Second switching bridge resistor R t2 Third switching bridge resistor R t3 Fourth switching bridge resistor R t4 Positive pole change-over switch K 1 Negative pole change-over switch K 2 ；
As shown in fig. 2, when detecting the bus insulation resistance in the dc system, the connection relationship between the detection circuit and the dc system is:
resistance to ground R + One end of the positive pole is connected with a positive pole change-over switch K 1 And a first switching bridge resistor R t1 Or the second switching bridge resistance R t2 Is connected in parallel to the ground resistor R + The other end of the first switching bridge resistor R is respectively connected with the first switching bridge resistor R t1 And the other end of the second switching bridge resistor R t2 The other end of the first and second connecting rods is connected;
by a first switching bridge resistor R t1 And a second switching bridge resistor R t2 Forming a first set of switches;
positive pole change-over switch K 1 And a resistance to ground R + One end of the positive pole U is connected into a direct current system + A common terminal;
negative resistance to ground R - One end of the negative pole is connected with a negative pole change-over switch K 2 And a third switching bridge resistor R t3 Or a fourth switching bridge resistor R t4 Is connected in parallel with a negative resistance to ground R - The other end of the first switching bridge resistor is respectively connected with a third switching bridge resistor R t3 And the other end of the fourth switching bridge resistor R t4 The other end of the first and second connecting rods is connected;
by switching the bridge resistance R t3 And a fourth switching bridge resistor R t4 Forming a second group of switches;
negative pole switchOff K 2 And a negative resistance to ground R - One end of the negative pole is connected into a negative pole U of the direct current system - A common terminal;
as shown in fig. 3, if the branch insulation resistance on the i branch in the dc system is detected, the connection relationship between the detection circuit and the dc system is:
the branch right-to-ground insulation resistance is recorded as R i+ One end of the positive pole is connected with a positive pole change-over switch K 1 And a first switching bridge resistor R t1 Or the second switching bridge resistor R t2 One end of (A) is connected in parallel, and the insulation resistance of the branch circuit facing the ground is recorded as R i+ The other end of the first switching bridge resistor R is respectively connected with the first switching bridge resistor R t1 And the other end of the second switching bridge resistor R t2 The other end of the first and second connecting rods is connected;
by a first switching bridge resistor R t1 And a second switching bridge resistor R t2 Forming a first set of switches;
positive pole change-over switch K 1 The insulation resistance right to the ground of the branch is recorded as R i+ One end of the positive pole U is connected into a direct current system + A common terminal;
the negative ground insulation resistance of the branch is recorded as R i- One end of the negative pole is connected with a negative pole change-over switch K 2 And a third switching bridge resistor R t3 Or a fourth switching bridge resistor R t4 One end of the branch is connected in parallel, and the negative earth insulation resistance of the branch is recorded as R i- The other end of the first switching bridge resistor is respectively connected with a third switching bridge resistor R t3 And the other end of the fourth switching bridge resistor R t4 The other end of the first and second connecting rods is connected;
by switching the bridge resistance R t3 And a fourth switching bridge resistor R t4 Forming a second group of switches;
negative pole change-over switch K 2 The insulation resistance from the negative earth of the branch circuit is recorded as R i- One end of the negative pole is connected into a negative pole U of the direct current system - A common terminal;
the branch right-to-ground insulation resistance is recorded as R i+ The other end of (2) and the branch negative-to-ground insulation resistance are recorded as R i- And the other ends of the two are all grounded.
In this embodiment, a method for detecting a bus insulation resistance based on a dynamic difference method is applied to the detection circuit, and is performed according to the following steps:
step a1, judging the voltage level of a direct current system, and if U =220V, executing step a2; if U =110V, executing step a3;
step a2: detecting the bus insulation resistance of a direct current system with the voltage grade of 220V:
step a2.1, closing the positive pole change-over switch K 1 First switch bridge resistor R t1 Resistance R opposite to the direct current system to ground + Parallel connection, in which case the DC ground fault finder is used to detect the current flowing through the first switching bridge resistor R t1 Has a current of I a Detecting the first switching bridge resistance R t1 Has a voltage of U at both ends 1+ The voltage at both ends of the negative ground resistor R-is U 1- Then, there are:
step a2.2, turning off the positive pole change-over switch K 1 Closing negative pole change-over switch K 2 Switching the third bridge resistor R t3 And a negative resistance to ground R of the direct current system - Parallel connection, at the moment, the DC ground fault finder is utilized to detect the current flowing through the third switching bridge resistor R t3 Has a current of I b Detecting the third switching bridge resistance R t3 Has a voltage of U at both ends 2- Just opposite to the ground resistance R + Has a voltage of U at both ends 2+ Then, there are:
step a2.3, simultaneous reaction of the formula (1) to the formula (4)Then, the positive ground resistance R is obtained by using the formula (5) and the formula (6) + And a negative resistance to ground R - ：
Step a3: detecting a bus insulation resistance of a direct current system with a voltage grade of 110V;
step a3.1, closing the positive pole change-over switch K 1 Second switching bridge resistor R t2 Resistance R opposite to the direct current system to ground + Parallel connection, at the moment, the direct current ground fault finder is utilized to detect the current flowing through the second switching bridge resistor R t2 Has a current of I a Detecting the second switching bridge resistance R t2 Has a voltage of U at both ends 1+ The voltage at the two ends of the negative-to-ground resistor R-is U 1- Then, there are:
step a3.2, turning off the positive pole change-over switch K 1 Closing negative pole change-over switch K 2 A fourth switching bridge resistor R t4 And a negative resistance to ground R of the direct current system - Parallel connection, at the moment, the DC ground fault finder is utilized to detect the current flowing through the fourth switching bridge resistor R t4 Has a current of I b Detecting the fourth switching bridge resistance R t4 Has a voltage of U at both ends 2- Just opposite to the ground resistance R + Has a voltage of U at both ends 2+ Then, there are:
step a3.3, obtaining the right-to-ground resistor R by using the formula (9) and the formula (10) after the formula (5) to the formula (8) are combined + And a negative resistance to ground R - ：
In this embodiment, a method for detecting a ground insulation resistance of a branch based on a dynamic difference method is applied to the detection circuit, and is performed according to the following steps:
step b1: judging the voltage level of the direct current system, and if U =220V, executing step b2; if U =110V, executing step b3;
step b2: detecting the insulation resistance of the No. i branch circuit to the ground in a direct current system with the voltage grade of 220V:
step b2.1, disconnecting the positive pole change-over switch K 1 Closing the negative pole changeover switch K 2 Switching to R t3 Detecting the voltage U of the positive bus i+ And collecting leakage current delta I of branch I i1 And has the following components:
step b2.2, closing the positive pole change-over switch K 1 Switching to R t1 Disconnecting the change-over switch K 2 Detecting the voltage U of the positive bus i ′ + And collecting leakage current delta I of the I branch i2 And has the following components:
after the step b2.3, the joint type (11) and the formula (12), calculating the insulation resistance R of the branch circuit to the ground by using the formula (13) and the formula (14) i ：
Namely:
delta U is the variation of voltage, and is equal to the difference between the voltage value of the positive electrode to ground when the measuring resistor is thrown into the positive bus and the voltage value of the positive electrode to ground when the measuring resistor is thrown into the negative bus, namely U' i+ -U i+ (ii) a Delta I is the variation of leakage current, and is equal to the difference between the branch leakage current value collected by the sensor when the measuring resistor is put into the positive bus and the branch leakage current value collected by the sensor when the measuring resistor is put into the negative bus, namely delta I = delta I i2 -ΔI i1 ；R i The resistance value of the branch circuit to the ground is a comprehensive equivalent quantity, which is equivalent to the parallel value of the insulation resistance value of the positive pole of the branch circuit to the ground and the insulation resistance value of the negative pole of the branch circuit to the ground in figure 1.
If the positive pole of the branch I passes through R i+ When being grounded, R i- Not grounded, respectively closed K 1 And K 2 Switching bridge resistor R t1 ，R t3 And similarly, two groups of positive bus voltage and branch leakage current values are measured. At this time, is U' i+ ＝0，ΔI i2 =0, obtained by using the formula (15)
If the positive pole of the branch I passes through R i+ Ground, R i- Ungrounded, i-1 branch positive pole passes through R (i-1)+ Ground, R (i-1)- Not grounded, respectively closed K 1 And K 2 Switching bridge resistor R t1 ，R t3 And similarly, the voltages of two groups of positive buses and the leakage current values of the branches I and I-1 are measured. At this time, is U' i+ ＝0，ΔI i2 ＝0，ΔI (i-1)2 =0, can be obtained by using the formula (15)
Step b3: switch off positive pole change-over switch K 1 Closing negative pole change-over switch K 2 Switching to R t4 Detecting the voltage U of the positive bus i+ And collecting leakage current delta I of branch I i1 And has the following components:
closed positive pole change-over switch K 1 Switching to R t2 On/off switch K 2 Detecting the voltage U of the positive bus i ′ + And collecting leakage current delta I of the I branch i2 And has the following components:
after the combination of the formula (16) and the formula (17), the branch circuit ground insulation resistance R is calculated by using the formula (18) and the formula (19) i ：
Claims (3)
1. A detection circuit of double-voltage-level direct-current insulation resistance based on a dynamic difference method is characterized in that the detection circuit is connected into a direct-current system, and the bus insulation resistance of the direct-current system is recorded as a positive ground resistance R + Negative resistance to ground R - (ii) a The branch circuit insulation resistance to ground on the I branch circuit of the direct current system is recorded as R i And the insulation resistance of the branch on the No. i branch facing the ground is recorded as R i+ And the negative earth insulation resistance of the branch on the I branch is recorded as R i- (ii) a The insulation resistance of the branch circuit on the I-1 branch circuit of the direct current system to the ground is recorded as R i-1 And the insulation resistance of the branch on the No. i-1 branch to the ground is recorded as R (i-1)+ And the branch negative earth insulation resistance on the i-1 branch is recorded as R (i-1)- ；
The detection circuit includes: first switching bridge resistor R t1 Second switching bridge resistor R t2 Third switching bridge resistor R t3 Fourth switching bridge resistor R t4 Positive pole change-over switch K 1 Negative pole change-over switch K 2 ；
If the bus insulation resistance in the direct current system is detected, the connection relationship between the detection circuit and the direct current system is as follows:
the resistance to ground R + Is passed through the positive electrode changeover switch K 1 And the first switching bridge resistor R t1 Or the second switching bridge resistor R t2 Is connected in parallel to a ground resistor R + Is connected with the first switching bridge resistor R t1 And the other end of the second switching bridge resistor R t2 The other end of the first and second connecting rods is connected;
by a first switching bridge resistor R t1 And a second switching bridge resistor R t2 Forming a first set of switches;
the positive pole change-over switch K 1 And the resistance to ground R + One end of the positive pole U is connected into a direct current system + A common terminal;
the negative resistance to ground R - One end of the negative pole is connected with the negative pole change-over switch K 2 Is electrically connected with the third switching bridgeResistance R t3 Or a fourth switching bridge resistor R t4 Is connected in parallel, the negative resistance to ground R - Is connected with the third switching bridge resistor R t3 And the other end of the fourth switching bridge resistor R t4 The other end of the first and second connecting rods is connected;
by switching the bridge resistance R by the third t3 And a fourth switching bridge resistor R t4 Forming a second group of switches;
the negative electrode change-over switch K 2 And the negative resistance to ground R - One end of the negative pole U is connected into a direct current system - A common terminal;
if the branch insulation resistance on the I branch in the direct current system is detected, the connection relationship between the detection circuit and the direct current system is as follows:
the insulation resistance of the branch circuit just facing the ground is recorded as R i+ Is passed through the positive electrode changeover switch K 1 And the first switching bridge resistor R t1 Or the second switching bridge resistor R t2 One end of (A) is connected in parallel, and the insulation resistance of the branch circuit facing the ground is recorded as R i+ Is connected with the first switching bridge resistor R t1 And the other end of the second switching bridge resistor R t2 The other end of the first and second connecting rods is connected;
by a first switching bridge resistor R t1 And a second switching bridge resistor R t2 Forming a first set of switches;
the positive electrode change-over switch K 1 And the insulation resistance opposite to the ground of the branch is recorded as R i+ One end of the positive pole U is connected into a direct current system + A common terminal;
the negative earth insulation resistance of the branch is recorded as R i- One end of the negative pole is connected with the negative pole change-over switch K 2 And the third switching bridge resistor R t3 Or a fourth switching bridge resistor R t4 One end of the branch is connected in parallel, and the negative-to-ground insulation resistance of the branch is recorded as R i- Is connected with the third switching bridge resistor R t3 And the other end of the fourth switching bridge resistor R t4 The other end of the connecting rod is connected;
by switching the bridge resistance R t3 And a fourth switching bridge resistor R t4 Form a second group of cutsChanging a switch;
the negative electrode change-over switch K 2 And the negative earth insulation resistance of the branch circuit is recorded as R i- One end of the negative pole is connected into a negative pole U of the direct current system - A common terminal;
the insulation resistance of the branch circuit facing the ground is recorded as R i+ The other end of (2) and the branch negative earth insulation resistance are recorded as R i- The other ends of the two are all grounded.
2. A bus insulation resistance detection method based on a dynamic difference method is characterized by being applied to the detection circuit of claim 1 and carried out according to the following steps:
step a1, judging the voltage level of the direct current system, and if U =220V, executing step a2; if U =110V, executing step a3;
step a2: detecting the bus insulation resistance of a direct current system with the voltage grade of 220V:
step a2.1, closing the positive pole change-over switch K 1 First switch bridge resistor R t1 Resistance R opposite to the direct current system to ground + In parallel, the DC ground fault finder is used for detecting the current flowing through the first switching bridge resistor R t1 Has a current of I a Detecting the first switching bridge resistance R t1 Has a voltage of U at both ends 1+ The voltage at the two ends of the negative-to-ground resistor R-is U 1- Then, there are:
step a2.2, disconnecting the positive pole change-over switch K 1 Closing negative pole change-over switch K 2 Switching the third bridge resistor R t3 And a negative resistance to ground R of the direct current system - Parallel connection, at the moment, the DC ground fault finder is utilized to detect the current flowing through the third switching bridge resistor R t3 Current ofI b Detecting the third switching bridge resistance R t3 Has a voltage of U at both ends 2- Just opposite to the ground resistance R + Has a voltage of U at both ends 2+ Then, there are:
step a2.3, obtaining the right-to-ground resistor R by using the formula (5) and the formula (6) after the formula (1) to the formula (4) are combined + And a negative resistance to ground R - ：
Step a3: detecting a bus insulation resistance of a direct current system with a voltage grade of 110V;
step a3.1, closing the positive pole change-over switch K 1 Second switching bridge resistor R t2 Resistance R opposite to the direct current system to ground + Parallel connection, at the moment, the direct current ground fault finder is utilized to detect the current flowing through the second switching bridge resistor R t2 Has a current of I a Detecting the second switching bridge resistance R t2 Has a voltage of U at both ends 1+ The voltage at both ends of the negative ground resistor R-is U 1- Then, there are:
step a3.2, turning off the positive pole change-over switch K 1 Closing negative pole change-over switch K 2 Switching the fourth bridge resistor R t4 And a negative resistance to ground R of the direct current system - Parallel connection, at the moment, the DC ground fault finder is utilized to detect the current flowing through the fourth switching bridge resistor R t4 Has a current of I b Detecting the fourth switching bridge resistance R t4 Has a voltage of U at both ends 2- Direct resistance to ground R + Has a voltage of U at both ends 2+ Then, there are:
step 3.3, obtaining the right-to-ground resistor R by using the formula (9) and the formula (10) after the formula (5) to the formula (8) are combined + And a negative resistance to ground R - ：
3. A method for detecting the ground insulation resistance of a branch circuit based on a dynamic difference method, which is applied to the detection circuit according to claim 1 and is performed according to the following steps:
step b1: judging the voltage level of the direct current system, and if U =220V, executing step b2; if U =110V, executing step b3;
and b2: switch off positive pole change-over switch K 1 Closing ofClosing negative pole change-over switch K 2 Switching to R t3 Detecting the voltage U of the positive bus i+ And collecting leakage current delta I of the I branch i1 And has the following components:
closed positive pole change-over switch K 1 Switching to R t1 On/off switch K 2 Detecting the voltage U of the positive bus i ′ + And collecting leakage current delta I of branch I i2 And has the following components:
after the combination of the formula (11) and the formula (12), the branch circuit insulation resistance to the ground R is calculated by using the formula (13) and the formula (14) i ：
Step b3: switch off positive pole change-over switch K 1 Closing negative pole change-over switch K 2 Switching to R t4 Detecting the voltage U of the positive bus i+ And collecting leakage current delta I of the I branch i1 And has the following components:
closed positive pole change-over switch K 1 Switching to R t2 On/off switch K 2 Detecting the voltage U of the positive bus i ′ + And collect the number iLeakage current Δ I i2 And has the following components:
after the vertical type (11) and the formula (12) are combined, the branch circuit ground insulation resistance R is calculated by using the formula (13) and the formula (14) i ：
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| CN116953360B (en) * | 2023-09-20 | 2024-01-19 | 上海派能能源科技股份有限公司 | Insulation resistance rapid detection method of energy storage equipment |
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