JPH0360320A - Inspection system for digital current differential protective relay - Google Patents

Abstract

PURPOSE:To remove the effect of the removal of fault, when inspection is carried out, by performing the inspection and judgment based on the differential current of each CT circuit used for differential protection if comparison of current values before and after the inspection does not present a value lower than a predetermined level which represents a satisfactory inspection result. CONSTITUTION:The total sum of the current from all CTs before inspection is SIGMAIL and the difference of the current between the CTs before inspection is Id. In the same way, the total sum of current after release of applied inspection current I is SIGMAI'L.I'd. Since SIGMAI is reduced if a fault is removed during inspection, the condition SIGMAIL-SIGMAI'L>K3 of a comparator 53 is satisfied. At this time, inspection at the reset side is confirmed through a comparator 54 based on the current differences Id and I'd, i.e., passing currents, which are not affected by an external fault current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inspection method for a digital current differential protection electrical device for protecting an electric power system.

(Prior Art) In a digital current differential protection relay device, the device must respond accurately in the event of a power system fault, and the device must not be defective. Even if there is a fault, the digital protective relay device is composed of a main detection relay and an accident detection relay, and when a system fault occurs, the specified response is performed when both outputs are present, and the device is designed to prevent errors. An automatic inspection function has been added as a measure to improve reliability against malfunctions on the operating side.

Figure 2 shows an installation example of a digital current differential protection device.

The current transformer consists of a main detection relay 15 that has a built-in current differential relay that operates when an internal fault occurs in the transformer Tr and deactivates when an external fault occurs, and an FD relay 16 that incorporates a current differential relay that has the same operating function. Inputs from CT1 and C70 are used to distinguish between internal and external faults, and in the case of an internal fault, a breaker (not shown) is tripped by the AND of the outputs of the main detection relay 15 and FD relay 16 to protect the system. .

FIG. 3 is a block diagram of the analog input circuit of the digital current differential protection relay device, and will be briefly described.

In FIG. 3, electrical quantities such as system current and voltage are applied to an input converter 41, and a checking electrical quantity 48 is applied to a filter 42 via an OR circuit 47. Sample hold circuit 4
3 samples the input electrical quantity at predetermined intervals, and converts it into a digital quantity by a multiplexer circuit 44 and a /D converter 45. The CPU arithmetic unit 46 is configured to perform predetermined digital arithmetic operations using the digital amount.

A general inspection method for conventional digital current differential protection relay devices will be specifically described below.

FIG. 4 is a flowchart of the entire inspection of the digital current differential protection relay device (hereinafter referred to as the device), and FIG. 5 is a flowchart of the inspection of the main detection relay and the fault detection relay.

First, the overall inspection will be described using Fig. 4.

In the figure, when an inspection start signal 1 is output, a trip lock command 2 is output, and then it is confirmed that the trip circuit of the device is trip locked. The raw detection relay inspection section 15 after trip lock confirmation consists of a main detection relay inspection process 4 that applies input for main detection relay inspection, etc., and a main detection relay inspection determination process 5.
After the defect storage process 12 and defect display device 14, the trip lock is released 9 by the inspection return command 8, and the inspection is completed. If the main detection relay inspection is satisfactory, perform the FD relay inspection. The FD relay inspection section 16 consists of an FD relay inspection process 6 that applies input for FD relay inspection, etc., and an FD relay inspection determination process 7, and when an inspection is defective, it passes through a defect storage process 13 and a defect display process 14, and then returns to inspection. Directive 8
6. If an accident occurs during the inspection, perform the trip lock release 9 and end the inspection.
The inspection return command signal 8 is outputted, the trip lock is released, the inspection is completed, and the power system is prepared for protection. For the determination of accident detection during inspection 11, the output of the FD relay is used during the main detection relay inspection, and the output of the main detection relay is used during the 0 relay inspection.The above is an explanation of the entire inspection.

Next, the responses of the main detection relay inspection section 15 and the GD relay inspection section 16, which are surrounded by a dot IR line in FIG. 4 and described in the above inspection, will be explained in detail using FIG. 5.

In the same figure, before starting the inspection, first the current data (
The preliminary power flow = IL) 21 is memorized, and then the operating side inspection current (IT) 22 is applied, and the current sum data (IL) 21 at that time is stored.
IL+IT) 23 is input to the determination unit 24. Subtract the memorized advance tide from that data (tidal flow cancellation),
Only the inspection current is obtained, and if the value is within the range of 1 to the predetermined level value ±, it is determined that the operating side inspection is good 25, and if it is outside the range, the t counter 26 counts up and the count value T2
If the count is more than that, it is determined that the inspection is defective and a defect storage process is performed. If the inspection is satisfactory, check current I as return side inspection.
T28 is canceled, the subsequent current data (1'L) 29 is input, and the current data (IL-1'L) obtained by subtracting I'L from the preliminary power flow (IL) is input to the determination unit 30,
It is determined whether the value is 2 or less at a predetermined level. If it is equal to or less than k2, the inspection is completed as return side inspection good 31. If it is greater than or equal to k2, the seven counter 32 counts up, and if it is greater than or equal to the count value T4, it is determined that the inspection is defective and a defect storage process is performed.

(Problem to be Solved by the Invention) A time chart will be used to consider the response to the inspection when an accident is removed during inspection of the main detection relay or the accident detection relay.

Figure 6 is a time chart when inspections are carried out normally on both the operating side and the return side.

FIG. 7 is a time chart when the accident is eliminated during the return side inspection.

A case where the inspection is carried out normally will be explained using FIG. 6.

Before starting the inspection, first check the current data (preliminary current = IL)
is memorized, and then a known inspection current (Iv) is applied by the operating side inspection input application command, and the current sum data (Iv) at that time is
Subtract the preliminary power flow (IL) from (L + IT) (power flow cancellation) to obtain only the known inspection current (■1), and confirm that this is the preset value of 1vk1 or more and Iv1/10 or less, and the inspection confirmation time (T1). ), it is determined that the inspection on the operating side is satisfactory, and the application of the known inspection current (Iv) is also canceled by issuing an inspection input application command. This will allow us to start checking the return side. The difference between the current (1'L) after the application of the known inspection current is canceled and the preliminary power flow (IL>) is 2 or less at the return judgment level, and the return side inspection confirmation time (T3) has continued. Then, it is determined that the return side inspection is satisfactory and the inspection is completed.

Next, a case where an external accident occurs before the start of the inspection and the external accident is removed during the return side inspection will be explained with reference to FIG.

The preliminary power flow (IL) has a value that includes the fault current, and is larger than the load current. When the inspection is started at this time, the operating side inspection is carried out in the same manner as in the case of FIG.

However, if the accident is removed by another protection device (not shown) during the recovery side inspection confirmation time (T3), the preliminary current (I
The current after canceling the known inspection current (I'L)
), the fault current is further subtracted, so the return side confirmation level will not be within 2 at the time of fault removal.
The return side inspection confirmation time (T3) does not count up, leading to an inspection failure.

The patterns that result in poor inspection have been described above, but if a fault in the power system is removed during inspection, it does not necessarily result in poor inspection. That is, as mentioned above, the device is composed of a main detection relay and 10 relays, and each relay is inspected separately. Therefore, during the main detection relay inspection, the inspection is disconnected by the operation of the 0 relay, and during the FD relay inspection, the inspection is disconnected by the operation of the main detection relay. It prevents it from happening. However, in the differential protection relay configured as shown in FIG. 2, since neither the main detection relay nor the FD relay operates in the event of an external fault, inspection and analysis cannot be performed, and the current change when the fault current is removed will result in an inspection failure.

Even if the device is found to be normal during inspections originally designed to discover defects in the device, it is a problem that the inspection becomes defective due to the elimination of faults in the power system, as this reduces the reliability of the device. As a countermeasure to the above, it is conceivable to incorporate a relay that operates on the principle of an external accident into the main detection relay or FD relay. However, installing a relay just to prevent inspection failures
There are disadvantages that the device cost is high and the device is complicated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an inspection method for a digital current differential protective relay device that does not affect fault elimination in a power system during input circuit recovery confirmation inspection.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention samples the analog electrical quantities corresponding to each phase of the power system at regular intervals and converts them into digital quantities. A differential protection relay device that performs digital protection calculations based on a predetermined calculation algorithm using the differential protection relay device applies a known inspection input at the time of inspection, compares the inspection input value calculated based on the calculation algorithm, Confirm that this current value is within the predetermined value range, then release the inspection input, compare the pre-inspection current and post-inspection current, confirm that this current value is below the predetermined value, and then perform the inspection. In the inspection method that determines that the current is good, if the comparison of the current value before and after the inspection is less than the specified value due to the removal of the fault in the power system, and the inspection does not become good, the differential current of each 01 circuit used for differential protection It was configured to carry out inspection judgments.

(Function) With the above configuration, defective inspections will not occur due to the effect of removing faults in the power system, and it can also contribute to improving the reliability of the digital differential protection relay device.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 is a flowchart of an embodiment for explaining an inspection method for a digital differential protection electrical device according to the present invention.

In FIG. 1, the same parts as in FIG. 5 are given the same reference numerals, and their explanation will be omitted.

When the operation side inspection is confirmed as good 25, 1. A release 28 is performed and an I'L input 29 is performed. In the present invention, IIL is performed here before entering the current value confirmation 30 of the return side inspection.

Id calculation 51. ΣI'L, r'd operation 52 is performed.

IIL is the sum of the currents of each 01 before inspection ΣIL=IL11
+1IL21+...Id is the difference current Id=I It1+IL2+...1 between the currents of each CT before inspection.

Similarly, Σ1'L and I'd are inspection applied currents 1. Total sum of current after release ΣI'L = l I'L1 l +
I I'L21+...1'd= l I'L1 +
I'L2+...1. Here, if an accident is removed during inspection, Σ■ decreases, so the condition for comparator 53 is ΣIL-Σ
I'L>k3 holds true. At this time, the comparator 54 confirms the recovery side inspection using the difference current Id and I'd, which are passing currents and are not affected by the external fault current. The confirmation level 4 is a value that takes into account the error of each CT.

Further, if the condition of the comparator 53 is not satisfied, it means that there is no external fault removal, and as before, IIL-1'L l<
By determining k2, it is possible to check with high accuracy a value of 2 that takes into account the error for C11. As explained above, by performing the recovery side inspection using a differential current when removing an external fault, it is possible to prevent inspection failures due to the effects of removing a system fault.

In the above embodiment, the inspection judgment based on the difference current Id is provided only for the return side confirmation, but the difference current 1d is also used for the operation side confirmation.
This inspection judgment is effective in preventing poor inspection judgments due to system accidents.

[Effects of the Invention] As explained above, according to the present invention, the advance trend (IL)
In an inspection method in which a known inspection current (■1) is memorized and a known inspection current (■1) is applied after the start of inspection, operating side inspection and recovery side inspection are performed.
The presence or absence of an external fault is determined using the sum current ΣI, and when there is an external fault, the return side inspection is determined by the difference current Id, so inspections can be performed without being affected by power system faults. , it is possible to provide a highly reliable inspection method for a digital current differential protective relay device.

[Brief explanation of drawings]

Fig. 1 is a flow chart for explaining the inspection method of the digital current differential protection relay device according to the present invention, Fig. 2 is an installation example of the digital protection relay device, and Fig. 3 is the digital current differential protection relay device. Figure 4 is a block diagram of the entire conventional inspection circuit, Figure 5 is a flowchart of conventional input circuit inspection, and Figure 6 is a diagram of the conventional input circuit inspection when the inspection completes normally. Time chart FIG. 7 is a time chart when removing a system fault during inspection in a conventional circuit inspection. 41... Input converter 42... Filter 43
... Sample hold circuit 44 ... Multiplexer 45 ... Analog-digital converter 46 ... Arithmetic unit 47 ... OR circuit 48 ... Electricity for inspection

Claims (1)

[Claims] A differential protection relay device samples the analog electrical quantity corresponding to each phase of the power system at regular intervals, converts it into a digital quantity, and uses this to perform digital protection calculations based on a predetermined calculation algorithm. Apply a known inspection input during inspection, compare the inspection input value calculated based on the calculation algorithm, confirm that this current value is within a predetermined value range, and then remove the inspection input. Therefore, in the inspection method that determines that the inspection is satisfactory by confirming that the difference between the current value stored before inspection and the current value after inspection input is removed is less than a certain value, each When the current sum of the CT circuits differs by more than a predetermined value between the stored value before inspection and the value after inspection, the difference current of each CT circuit is used when determining the difference between the stored value before inspection and the inspection input removed. An inspection method for a digital current differential protective relay device characterized by the following.