JPH04200224A - Inspection system for digital protective relay - Google Patents

Abstract

PURPOSE:To obtain an inspection system for digital protective relay which can be applied even on a system having significantly short time variation of tidal current by making the value for judging defective inspection variable with the variation of tidal current. CONSTITUTION:A setting circuit 9 sets a tidal current variation alpha in a system. A CPU operating circuit 8 performs operation shown by formula 1 at step 8a and then performs operation shown by formula 4 while taking account the variation alpha of tidal current at step 8b. Operation shown by formula 5 is then performed at step 8c while taking account the variation alpha of tidal current. Results at steps 8b, 8c are then judged at step 8d. In case of acceptable inspection, the control proceeds to step 8e where 'I-level OK' is set and then an inspection counter is counted up at step 8f thus completing inspection. Otherwise, the control proceeds to step 8g where 'I-level NO' is set and the defective inspection is alarmed externally at step 8h thus completing the inspection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inspection method for a digital protective relay device when there is a fluctuating load on the grid side.

(Prior Art) Referring to FIG. 3, a method of inspecting an analog input circuit that is generally performed in a digital protective relay device will be described.

The analog input circuit includes an input converter 1, a filter circuit 5, a multiplexer circuit M6, and an analog-to-digital conversion circuit 7.
It has the function of introducing current and voltage data for protection calculation of the protective relay device into the CPU calculation circuit 8, and is the most important circuit in the protective relay device. Regarding voltage data, since the rated amount of electricity is always applied, it is possible to detect abnormalities through constant monitoring, but because the level of current data varies depending on the system operation status, it is possible to detect abnormalities in the circuit by inspection. It is absolutely necessary to confirm that there is no such thing. During this inspection, the inspection input application circuit 3 is closed in response to an inspection command, and the output of the inspection input oscillation circuit 2 is supplied to the inspection input superimposition circuit 4.6 The inspection input superposition circuit 4 inputs the amount of grid electricity from the input converter 1 to the inspection input superimposition circuit 4. The inspection input amount from the application circuit 3 is superimposed, and the superimposed electrical amount is introduced into the CPU arithmetic circuit 8 via the filter circuit 5, the multiplexer circuit 6, and the analog-to-digital conversion circuit 7.

The CPU arithmetic circuit 8 performs software arithmetic processing as an analog input check as shown below.

In step 8a, the amount of electricity input to the digital relay at the time of zero inspection in which power flow cancellation processing is executed is, as described above, a vector combination of the amount of inspection input (ITS) and the amount of system electricity (■,).

The system electricity amount (I,) can change depending on the system operation status, and it is necessary to exclude it in order to know the level of the inspection input amount (ITs). The purpose can be achieved by effectively utilizing the data memory function unique to digital relays and calculating equation (1).

Inspection dark current Pre-inspection current ITS...Inspection input component I', I', I'...Each sum pre-current RL
SL TLIRL, ISt”
TL...Each phase power flow component I, I, during inspection
IT...Determined power flow cancellation S for each phase In the following component (1) equation, since there is no sudden change in power flow in a normal system, RL is
RL Yes, each phase component after power flow cancellation (I, I.

S I) are all obtained as inspection input components (11S)■ Ru.

In step 8b, a relative value level check is performed.

Focusing on the fact that the inspection input is the in-phase input to each phase, (1
) It is confirmed that the phase relationship between each phase is correct by calculating the equation (2) using the data obtained from the equation.

In equation (2), ε0 indicates the inspection defect determination level. As a specific numerical example, relay hard error (1 to
2%), soft performance! It is set at about 15% of the inspection input, taking into account about twice the margin as the total (5 to 7%) of errors (1 to 2%) and relay external condition errors such as frequency fluctuations (3%). There is.

In step 8C, an absolute value check is performed.

In relative value checking, the phase relationship and relative level between each phase are checked, but the absolute level cannot be checked.
) Confirm that the absolute value level is correct by calculating equation (3) using the data obtained from equation.

K < l I Hl < K2 f3) Formula (
3) In the formula, 1 indicates the lower limit judgment level and K2 indicates the upper limit judgment level. Considering relay input errors, etc., the lower limit value is usually 85% and the upper limit value is 85% of the inspection input level (I, S). It is set at about 115%. The basis for setting the level of K and 2 is based on that of ε0 described above. In addition,
Since the relativity of each phase is confirmed by a relative value check, an absolute value check is performed on a representative phase (for example, R phase).

In the 8d step, the results of the 8b step and 80 step are determined. If the inspection is good, proceed to step 8e and “I-
Set the level to OKJ and set the inspection counter to UR in 8f steps.
L. Finish inspection. If not, proceed to 8g step [I
- Set the level to NOJ, issue an external alarm for inspection failure in 8-hour steps, and complete the inspection.

The above is an overview of the analog input circuit inspection software processing.

(Problems to be Solved by the Invention) The conventional inspection method described above uses a power flow cancellation algorithm as the basis of calculation.

As mentioned above, this is achieved by subtracting the pre-inspection current from the inspection dark current, and is an algorithm designed to ensure that the current does not suddenly change in a short period of time.

In ultra-high voltage systems (275 kV or higher), there are no sudden changes in power flow, so there is no time difference even with conventional inspection methods, but in low-voltage systems (15 kV or higher)
4kV or less), it has become clear that this power flow fluctuation cannot be ignored. Particularly in cases where there is factory equipment such as a steel mill near the system, the difference between the preliminary power flow (I') and the power flow component (IRl) at the time of inspection becomes large, and with conventional inspection methods, even if the equipment is normal, Inspection failure may occur regardless of the situation.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an inspection method for a digital protective relay device that can be applied even to systems where short-term fluctuations in power flow are significant.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention is configured such that the inspection failure determination value can be varied in consideration of the value of the power flow fluctuation.

(Function) Therefore, the inspection failure judgment value can be varied and set even in systems with power flow fluctuations, so the optimum inspection failure judgment level can be set for power flow fluctuations that vary in level for each system.
It becomes possible to inspect the analog input circuit of the protective relay device.

(Example) Hereinafter, the present invention will be described in detail with reference to FIG. 1st
The basic structure of the figure is the same as that of FIG. 3 already explained, and the same contents are given the same reference numerals and the explanation will be omitted. Reference numeral 9 denotes a settling circuit, which settles the power flow fluctuation (α) in the system. Note that the setting circuit is a circuit that is always provided in a digital protective relay device, and the configuration is such that only one setting element is added thereto. And CPU calculation circuit 8
Now, the power flow variation (α) determined above is introduced and processed by the following software calculation.

In step 8a, the above-mentioned equation (1) is calculated.

In step 8b, equation (4) is calculated taking into consideration the power flow variation (α) due to the above-mentioned setting.

In equation (4), ε. is equal to the conventional inspection defect determination level described above, and this time, the power flow fluctuation amount (α) is added to this to perform a relative value inspection defect determination level.

In the 8C step, the power flow fluctuation due to the above setting (α
) is taken into account to calculate equation (5).

K − α ] I 1 K + α (5) Equation 1 Equation % In Equation (5), K 1. K2 indicates the lower limit judgment level and upper limit judgment level in the conventional inspection described above, and this time, the power flow fluctuation (α) is subtracted from this to the lower limit value and added to the upper limit value to determine the absolute value inspection failure. It is for making judgments.

Processing for steps below 8d is performed in the same manner as in the conventional inspection method described above.

FIG. 2 shows another embodiment of the present invention. The difference from FIG. 1 is the content of the setting circuit 9, which will be explained. In the embodiment shown in FIG. 1, the power flow variation (α) is provided as an individual setting item, but in this embodiment, the variation width setting of the current variation detection element (hereinafter referred to as ΔI element) is shared.

The ΔI element responds to changes in each phase current, and responds sensitively to power flow fluctuations.Normally, it is fixed at about 10% of the rated current, but if the power flow fluctuations are significant, In this embodiment, the inspection failure determination level is changed in conjunction with this variable setting value (α). Since the setting of the ΔI element is □, which excludes the power flow fluctuation, the effect is similar to that of the embodiment shown in FIG. 1, and the advantage is that there is no need to newly provide individual setting items. Although this embodiment is limited to a protective relay device with a built-in Δ■ element, in a low-level system where power flow fluctuations are significant, a digital protective relay using a distance relay method with a built-in Δ■ element can be used. Since electrical devices are the mainstream, the effect is significant.

[Effect of the invention] As explained above, according to the present invention, the power flow fluctuation (α)
is input to the digital relay by setting, and the inspection failure judgment level is variable, so the inspection function of the digital protective relay device can be maximized not only in systems with no power flow fluctuations, but also in systems with significant power flow fluctuations. It is possible to provide an inspection method that allows the equipment to be operated effectively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment of the present invention, and FIG. 3 is a block diagram of a conventional device.

Claims (1)

[Claims] Analog electrical quantities corresponding to each phase of the power system are sampled at regular intervals, converted to digital quantities, and digitally calculated based on a predetermined calculation algorithm to determine operation and protect the power system. In such a digital protective relay device, a check input is applied to the analog input circuit, an amplitude value is calculated based on the calculation algorithm, and the difference between this amplitude value and the check input is within the check failure judgment value. 1. An inspection method for a digital protective relay device, characterized in that when determining that the inspection is good, the inspection failure judgment value is varied.