[Endian Electric] Microcomputer relay protection test system wiring check

Microcomputer relay protection tester wiring check:

Differential protection is widely used in power systems in transformers, buses, and short-circuit protection. General differential protection simulation test is more difficult, mainly for the following reasons: First, the differential protection of the current loop is more, two-turn transformer needs high and low voltage on both sides of the current, three-turn transformer needs high, medium and low voltage three-side current Bus protection needs more; Second, the core of differential protection is to provide differential relays for differential relays or automation systems. It requires that the polarity of each current loop must be correct; otherwise, the polarity will become wrong. And current; Third, the characteristic test of differential protection is more difficult.

For example, transformer differential protection is constructed by comparing the amplitude and phase of the currents on both sides of the transformer. The current transformers on both sides of the transformer are connected by differential connection. In normal operation and external faults, the current flowing into the relay is the difference between the currents on both sides. The value is close to zero and the relay does not operate. In the event of an internal fault, the relay flows in. The current is the sum of the currents on both sides. The value is the short-circuit current and the relay operates. It can be seen that the correct connection of current transformers on both sides of the transformer directly affects the operational reliability of longitudinal differential protection.

In the microcomputer relay protection system, usually the secondary winding of the current transformer has two wiring forms, ie, the current wiring form and the differential current wiring form. Differential current wiring is characterized by the reverse polarity of a set of current transformer secondary windings connected with the other group, the so-called circulating current method wiring. Checking whether the current transformer wiring is correct is a work that relay protection workers often perform. The use of a clamp meter can directly detect and display the phase relationship of each current and voltage loop, thereby determining whether the wiring status is correct, reducing the workload of the testing personnel, and improving Work efficiency.