JPS6115520A - 2-wire defect 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 (Field of Industrial Application) The present invention relates to a protective relay that detects two-wire faults such as two-wire short circuit faults and two-wire ground faults in power systems.

(Prior art) A short-circuit protection relay that detects a two-wire fault has a delta voltage V, -
Impedance ZR due to V6 and delta current R-8
It is determined by comparison that Y is smaller than the set value z8.

(Problems to be Solved by the Invention) Conventional short-circuit protection relays are capable of preventing two-wire short-circuit failures and two wires at the same point.
In the case of a line-to-ground fault, the correct line impedance up to the fault point can be detected and a protective output can be obtained, but in the case of a different-point, different-phase ground fault, the correct impedance cannot be detected and the nearest fault point is the first stage of the distance relay. There is a problem in that even if one is within the operating range, the other, more distant fault point is outside the operating range and becomes inoperable.

In the resistive grounding system shown in Fig. 2, Fig. 3 (At and (Bl) indicate the two-wire fault vector at the same point, of which (AI) indicates the two-wire short-circuit condition, and (B) indicates the two-wire ground fault condition. , and these vectors can be reliably detected as long as they are within the settling range as a result of calculation of equation (1) by the distance relay RY.However, as shown in Figure 2, the R phase of the line IL is Within the operating range (set zs to 8 of the line length)
When a ground fault occurs on the power receiving side (outside the operating range) and a ground fault occurs on the 8th phase on the receiving side (outside the operating range), the vectors at relay RY of line 1 have the relationship as shown in Figure 3 (a). , impedance zR seen from relay RY
Y becomes larger than the set value z6 and becomes inoperable even though it is within the operating range due to the R phase fault force.

As described above, in a relay whose protection range is approximately 80 mm of the line length, if the protection calculation is performed using the equation (1) above, the relay may become inoperable in the event of a ground fault at a different point or in a different phase. in this case,
As a backup measure, this will cause a timer trip for the second and third stages of the distance relay, resulting in a delay in clearing the fault.

(Ninth Means and Effects for Solving the Problems) The present invention detects a two-wire short circuit fault by comparing and determining the impedance determined from the voltage and current of the two wires, similar to the conventional distance relay, and detects a two-wire ground fault. A fault is determined by comparing the magnitude of impedance obtained from the voltage and current of each line, and when a fault is determined for one of these comparisons, a protective output for a 2-wire fault is obtained. It is possible to detect faults including ground faults at different points and different phases.

(Example) FIG. 1 is a circuit diagram showing one embodiment of the present invention.

Distance relay element 1 is connected to voltages V, , V8 of two phases of the system and current line 8. Engineering. is input, the impedance ZR8 is determined according to the above formula (1), and this impedance ZRt3 and the setting value Z8. A two-wire short circuit fault is detected by comparing the size with the two wires. Distance relay element 2.3 separately detects phase voltage vR1vs and phase current 8. for R phase and S phase. Engineering, from next (3).

Find the impedance ZR, Z, 3 according to formula (4),
This impedance ZR, z8 is set to a setting value Z6. *z
A ground fault or short circuit fault in each phase is detected by comparing the magnitude with 88.

■ ZR”' r, ・・・・・・・・・(3)z,,
, = Koei Engineering. °・・・・・・・・・(41 OR circuit 4 obtains the logical sum output of elements 2 and 3, and detects that there is an operating output in either one. Undervoltage element 5 and earth fault overvoltage element 6 The undervoltage and overvoltage of the R and S phases are detected.The AND circuit 7 obtains the AND output of the elements 5.6, and detects a two-wire ground fault when undervoltage and overvoltage occur.

The AND circuit 8 obtains a logical product output of the output of the OR circuit 4 and the output of the AND circuit 7, and makes the output of the distance relay element 2 or 3 valid only in the event of a two-wire ground fault.

The OR circuit 9 obtains a logical sum output of the output of the element ] or the output of the AND circuit 8, and obtains a two-wire fault detection output.

Therefore, in the event of a 2-wire short circuit fault, the distance relay element 1 maintains its operation by the output, and in the event of a 2-wire ground fault, the distance relay element 2
Or, the protection operation is performed by output No. 3, and two-wire faults including different point and different phase ground faults can be detected and the protective output can be obtained.

In the embodiment, the undervoltage element 5 and the earth fault overvoltage element 6 used for detecting a two-wire ground fault are used for detecting a two-wire ground fault, but they may be obtained from outside the device.

(Effects of the Invention) According to the present invention, short circuits in 2 wires and ground faults in 2 wires at the same point are detected by a distance relay element that is within its operating range based on delta voltage and current, and ground faults at different points and in different phases are detected by a relay element that is within its operating range. The voltage and current of each line are detected by distance relay elements respectively.

Since a protection output for a two-wire fault is obtained by detecting one of the two relay elements, any fault can be reliably detected and tripped immediately as long as it is within the protection range. There is no delay in clearing faults due to back-up protection due to different-phase ground faults at different points.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a system diagram involving a different phase ground fault at different points, and Figs. 3 (A) and 3 (B).
l is a vector diagram at the time of a two-wire fault at the same point, Figure 3 (cl is a vector diagram at the time of a different phase ground fault at different points. 1.2, 3... Distance relay element, 4, 9... OR circuit , 5... Undervoltage element, 6... Earth fault overvoltage element, 7
．． 8...AND circuit. Figure 1 Figure 2 Figure 3 (A) Figure 3 CB) Figure 3 (C)

Claims (1)

[Claims] For a two-wire short-circuit failure in a power system, two-wire voltages V_R and V_S are used.
and the impedance Z_R obtained from the currents I_R and I_S.
_SZ_R_S=(V_R-V_S)/(I_R-I_
Compare and judge whether S) is larger than the set value, and in case of a two-wire ground fault, one impedance Z_R, Z_S calculated from the voltage and current of each phase. A two-wire fault protection relay characterized in that it compares and determines whether the difference is larger or not, and obtains a two-wire fault protection output when one of these comparisons yields a fault determination.