JPS59226614A - Power source for stationary protecting relay - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] This invention relates to a power supply device for a static protective relay. Normally, an electromagnetic protective relay (hereinafter referred to as an electromagnetic relay) is constructed so that the relay itself operates in the event of an accident. However, in recent years, electromagnetic relays have been replaced by static protective relays (hereinafter referred to as static relays) made of transistors, etc. due to their characteristics, large size, and maintenance aspects. I'm starting to think about it. Since static relays are formed from electronic circuits such as transistors and computers, they cannot operate unless power is supplied to the electronic circuits. Therefore, a DC power source is required. This DC power supply is installed in power plants and large-scale substations to operate circuit breakers, disconnectors, transformer tap changers, etc. is convenient. However, DC power supplies are rarely installed in small-capacity customers, substations, etc. 7 Because of this, a DC power source must be created in order to install static relays in the above-mentioned customers. An example of this method is to obtain DC power from a DC power supply in a distant power plant or large-scale substation using a long line. Figure 1 shows how this method can be applied to a loop system. In the diagram, AC
is a large-scale substation. Power lines BIL and BU* are connected in a loop to bus bar BU connected to this substation AC. A-D are consumers, each consumer A-1)
A stationary relay TRY is installed. These relays TRY are equipped with a DC power supply D installed in the substation and AC.
DC power is supplied from C through DC power supply lines ps, , ps,. CT, , CT is a current transformer that obtains the information of the static relay TRY, and this current transformer CT, ,
The information signal detected by the CT is input to the stationary relay TRY.

DC power is supplied to the static relay configured as shown in FIG. Since the PS network is relatively long, it has drawbacks such as a voltage drop and large voltage fluctuations due to the supply to several customers (four locations in the figure) A to D.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a power supply device for a protective relay that can obtain DC power to be supplied to a stationary relay in the vicinity of the relay.

An embodiment of the present invention will be described below with reference to FIG. 2. FIG. 2 shows the current transformer CT shown in FIG.

CT and the details of the static relay TRY are shown in detail. Note that since the current transformers CT and CT have the same configuration, only the current transformer CT will be described in FIG. R,
S and T are three-phase power lines, and the three-phase power lines R, S, and T are equipped with ground fault relay information detection current transformers ZCT, and the power line R and T phases are equipped with short circuit relay information detection current transformers CTR. And CT?
is provided. These current transformers CTFI, CTte, Z
A first auxiliary current transformer AUX+, AUX嘗, AUXs is provided on each secondary side of the CT. This first auxiliary current transformer AUX1
Resistors RI-R1 and R- for converting current into voltage are connected in parallel to the secondary sides of AUXI and AUX-, respectively. Overvoltage blocking varistors vs, , vs, , VSs are connected in parallel to the resistors R, , R, , R,. Said first auxiliary current transformer AUX+-AUX snow, AUX
One end of each secondary side of . . A smoothing capacitor C and a Zener diode ZD are connected in parallel to both common connection points, and both ends of the capacitor C and the Zener diode ZD are connected to a constant voltage circuit AVH.

The output voltage of the constant voltage circuit AVH is supplied to the central processing unit CPU, multiplexer MPX, and analog-to-digital converter A/D that constitute the static relay TRY. The multiplexer MPX includes a second auxiliary current transformer A CTI,
Protection information is input via the ACTs. O/E is an optical-to-electrical converter, and protection output data is sent out via this converter 0/B.

FIG. 3 is a circuit diagram showing details of the first auxiliary current transformer AUX+, in which a limiter LM consisting of a diode is provided on the primary side of the first auxiliary current transformer AUX, and this limiter L
M is used to limit the current when a large current exceeding a certain level, such as a short circuit current, occurs. In addition, since there is a varistor vSi on the secondary side of the first auxiliary current transformer AU
is not applied.

Next, the operation of the above embodiment will be described. 3 phase power line R2S, T
When the load current flowing through is equal to or greater than a predetermined value, a predetermined current is obtained on the secondary side of the first auxiliary current transformers AUX+ and AUX-. This current flows through resistors R+ and Re, and a voltage is generated across them. This voltage is rectified by rectifiers RfI and Rf, smoothed by a smoothing capacitor C, and becomes a DC voltage stabilized by a Zener diode ZD. The DC voltage thus obtained is supplied to the constant voltage circuit AVR, where it is further stabilized, and then supplied to the static relay TRY.

As shown in FIG. 4, it has been experimentally confirmed that a predetermined DC voltage V can be obtained if the load current is 1 A or more. This fourth
From the figure, when the load current becomes 1A or less, the specified DC voltage +
Although V cannot be obtained, there is no need for protection relays, not just static relays TRY, to perform their functions in the above-mentioned state, so there is no problem with separate installation. However, if an accident occurs during a no-load state, it must perform its function as a protective relay, but in this embodiment, DC power is obtained by the flow of the fault current, so this power supply is used to The type relay TRY becomes operable and protection can be ensured.

For example, DC power can be obtained in either a three-phase short circuit accident or a two-phase short circuit accident. In addition, even in the event of a ground fault, current transformer Z
If a current of about 1 A flows through the secondary side of the CT, a DC voltage +V can be obtained as is clear from FIG. 4, and as a result, protection against short circuits and ground faults can be ensured.

As described above, according to the present invention, the DC power supply to the static relay is rectified by converting the current from the current transformer that obtains the information of the protective relay, and the rectified voltage is stabilized. Since the power is supplied to the static relay, a stable DC power source can be obtained reliably depending on the load current, short-circuit current, and ground fault current without having to install a DC distribution line exclusively for the static relay over a long distance. This has the advantage of not reducing the reliability of direct current power supply, and also provides reliable protection against various accidents.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration of a loop system showing a conventional example, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a circuit diagram showing details of an auxiliary current transformer, Fig. 4 is a characteristic diagram of DC voltage with respect to load current.

Claims (1)

[Claims] (1) A current transformer installed on the power line to obtain the information signal of the protective relay, an auxiliary current transformer installed on the secondary side of this current transformer, and a current transformer installed on the secondary side of this auxiliary current transformer. A current-to-voltage converter that converts the current obtained by the converter into voltage, a smoothing circuit that rectifies and smoothes the voltage obtained by this converter, and a stabilizing circuit that controls the output of this smoothing circuit to a stable voltage. A power supply device fl for a static protective relay, characterized in that the DC output voltage of the stabilizing circuit is supplied to a protective relay.