Four connection methods of electromagnetic current transformer
Through the previous study, I have understood the basic principle structure, transformation ratio, capacity, accuracy level and precision of electromagnetic current transformers. This chapter will briefly introduce several common wiring methods of electromagnetic current transformers; 1 .Single-phase wiring, as shown in the figure: This wiring consists of only one current transformer, the wiring is simple, and is not commonly used in power supply systems. 2. Incomplete star connection, as shown in incomplete star connection, also called two-phase V-shaped connection, according to the three-phase electricity calculation formula IBu003d-(Ia+Ic), only need to measure the A-phase current and C-phase current , the current flowing in their common return line is the B-phase current. (1ka shows A-phase current 2ka shows B-phase current 3ka shows V-phase current). Not commonly used in power supply system, incomplete star connection is often used in 6-10kV neutral point not directly grounded three-phase three-wire system 3. Two-phase current difference connection, as shown in the two-phase current difference connection, measure A and C respectively For phase current, connect S1 of phase A to S2 of phase C. In theory, when there is no fault in the circuit, Iau003dIc, and the current angle of phase C is negative 120 degrees, so Ka has no value displayed. ①When the AB phase is short-circuited, the A phase CT detects the fault current, and the Ka has the fault current display. ②When the AC phase is short-circuited, the A and C phase CTs detect the fault current respectively, and the Ka has the fault current display. ③ When the BC phase is short-circuited, the C phase CT detects the fault current, and the Ka has the fault current display. The two-phase current difference wiring method can only be used in the low-current grounding system in the power system. When a ground fault occurs in any phase, since it is a low-current grounding system, it is allowed to run for 2 hours with the grounding point, so no tripping is required. 4. Three-phase star connection, as shown in the three-phase star connection, this connection method is relatively common and widely used in the entire power system. It can measure the three-phase current of the circuit and monitor the load asymmetry of each phase.