JPS62250820A - Three-phase differential 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 [Technical field to which the invention pertains] The present invention relates to a three-phase differential relay for detecting an internal short circuit occurring in a three-phase device such as a three-phase generator.

[Prior art and its problems] FIG. 3 shows an example of a conventionally known ratio differential relay. In this figure, Wl, Wl.

W is the secondary winding of the three-phase generator, Rq is the grounding resistor,
CT8, , CTA2, CTB,
, CT[12, CTCl.

CTC2 is the main CT (current transformer) provided at both ends of the protection zone, DR8, 0110, [1II
C are active side input terminals (ial-fa2.
f bl -jb2. t cl-ic2) and the inhibitory input current (tal+ i a2゜fbl+ tb
2. It is a single-phase ratio differential relay that operates based on icl+tc2).

In Fig. 3, each single-phase ratio differential relay DR^,
DIIB and DnC determine that a change has occurred and operate when the following operation formula is satisfied.

That is, for the relay DRA, the operating formula is l ja
l-! a21-111 tat+ 1a21 >A.

Here, K is a constant (0< to <
l), A is the operating threshold.

However, due to an external accident, an excessive current flows into the winding w1.
．． W2. If the current flows through W3, an error current due to CT saturation will flow into the differential circuit.

As a result, the relay may malfunction despite the compensation provided by the suppression input terminal.

[Object of the Invention] Therefore, the object of the present invention is to provide a three-phase differential relay configured to compensate for the error current of the differential circuit caused by the saturation of the CT and to prevent malfunction even in the event of an external fault. It is about providing.

[Key Points of the Invention] When a CT becomes saturated due to excessive current caused by an external accident, etc., and current flows through the differential circuit, current also flows into the secondary residual circuit of the Y-connected CT. The current is used to compensate for the differential circuit current generated due to CT error.

That is, the three-phase differential relay according to the present invention introduces outputs corresponding to the inflow and outflow currents of each of the three phases from a pair of Y-connection main current transformers provided across the protection zone, and current detection means for detecting dynamic current for each of the three phases; first detection means for detecting and outputting the maximum differential current among the differential currents for the three phases; and a pair of Y-connected main transformers. A second detection means and a third detection means for detecting and outputting the passing current of each residual circuit in the flowmeter and the output data of the first to third detection means are introduced, and output data satisfying a predetermined operation formula is obtained. and a determination means that outputs a message to that effect when the determination is made.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a schematic configuration diagram showing an embodiment of a three-phase differential relay to which the present invention is applied, and FIG. 2 is a block diagram showing its detailed configuration.

In FIG. 1, the same components as in the conventional example shown in FIG. 3 are given the same reference numerals. Therefore, the part unique to this embodiment is the part ny surrounded by a broken line. Here, 14~
18 is the primary winding of the CT inserted into the differential circuit, and 20
and 22 indicate the primary winding of a compensation CT provided to detect the current flowing in the residual circuit on the secondary side of the main C7.

In addition, in FIG. 2, 30 to 38 are each phase differential current ia
d, ibd, k cd and residual circuit current 1°1
40 is a maximum value extraction circuit, 42 is a determination circuit, and R1 to R5 are resistors.

The maximum value extraction circuit 40 outputs the maximum absolute value of the difference current between the inflow current and the outflow current in each phase as the operating side human power (differential) current 1d.

That is, rd-(11al-tazl, 11bt-1bz
l.

11 cl -'1 c2 l 1max rectifier circuit 36
and from 38, the residual circuit current ″Xol and i 0
Since the absolute value of 2 is 110 degrees and 11 degrees, 1 is obtained, the determination circuit 42 energizes the auxiliary relay 44 when the operation formula Id-l 1otl-l 1o21>A is satisfied.

Here, A is a constant for setting the operating value of one-end inflow.

In this way, this embodiment adopts a three-phase integrated configuration, and uses the current flowing in the residual circuit on the secondary side of the CT to
This cancels the differential circuit current caused by errors.

[Effects of the Invention] As described above, according to the present invention, the current flowing in the residual circuit on the secondary side of the CT is used to compensate for the differential circuit current caused by the error current of the CT. The difference that occurs in the event of an accident! ! Malfunctions of the JJ relay can be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing this embodiment in more detail, and FIG. 3 is a diagram showing the prior art. W1 to W3... 3-phase generator winding, 11G... Grounding resistor, (:TAL, to CT8, cTe, , CTB2
, CTCl, cTe2...Main current transformer (CT), DRA, Dll[1, Dn[:...Single-phase ratio differential relay, 14-22...-CT primary winding, Ry... 3-phase differential coupling TL device, 30-38... Rectifier circuit, 40... Maximum value extraction circuit, 42... Judgment circuit, 44... Auxiliary relay. ω0

Claims (1)

[Claims] 1) Outputs corresponding to the inflow and outflow currents of each of the three phases are introduced from a pair of Y-connected main current transformers provided with a protection zone in between, and the differential current is transmitted between the three phases. current detection means for detecting each of the respective phases; first detection means for detecting and outputting the maximum differential current among the differential currents for the three phases; and each of the pair of Y-connected main current transformers. A second detection means and a third detection means that detect and output the passing current of the residual circuit, and output data of the first to third detection means are introduced, and output data that satisfies a predetermined operation formula is obtained. A three-phase differential relay comprising: and a determination means for outputting a determination means to that effect.