Custom china

(A) transformer connection group

Mark used by the polarity of the transformer polarity mark. Polarity is marked by the same core column two windings in a moment of relatively high or relatively low potential point of the same polarity as potential points, marked with the same name side \"A\", \"a\" or \"*.\" Using subtractive polarity mark, when the winding current from the original \"A\" flow, the secondary winding current by \"a\" out. The transformer winding connection group is a three-phase power transformer primary, secondary line voltage corresponding to the phase relationship between the use of clock notation. Minute hand on behalf of the original edge voltage phasor, and the exceptionally fixed point 12, the clock on behalf of Vice-edge voltage of phase corresponding to the amount of points is a few minutes to point wiring.

(B) to determine the differential protection of transformers and wiring connection group

Be easy to determine, assuming that the transformer connected with purely resistive load, the original, any phase of the secondary winding voltage and the root of the current in the same phase winding. The same column of the original core, the secondary winding current of the same phase, that is primary from the \"A\" end into the secondary side by the \"a\" side out, transformer wiring as shown in Figure 1, the phasor diagram shown in Figure 2. UA set for the primary phase voltage reference, point 12, the primary phase currents IA and UA with the same core columns of the original, with the secondary winding of the current phase of both sides of the root of the corresponding phase voltage Ua and flows through the windings of the the same phase current Ia. To determine the wiring for the Y/Y-12 wiring group.

Transformer differential protection during normal operation and external fault, poor loop current flows on both sides of the transformer and current transformer secondary current. Both sides of the transformer current transformer can be into two three-phase power line to the three-phase load – three differential relay power supply. If two opposite phase power supply current is flowing into the load current phasor and zero. Connection shown in Figure 3, the transformer high voltage side of the LH current transformer connected to Y/Y-12, low-voltage current transformer LH then pour into Y/Y-6. Then both sides of the measuring current transformer secondary current of the same name with IA2 and Ia2 opposite phase. Shown in Figure 4. Inflow of poor loop phase current transformer secondary current and the same name. If the transformer score. Equal to both sides of the current transformer ratio nB = nLH = WLH \\ / WLH, loop current flows into the difference is zero, that is, IA2 ten Ia2 = 0.

Y / Δ-11 wiring transformer, the transformer primary current IA behind the secondary current Ia30?, Even if both sides of the current transformer circuit current values ??into the difference equal to the difference circuit is still an imbalance in the current Ibp = 2I2sin30 ? / 2. Eliminate this imbalance is the current Y-connection side of the transformer current transformer connected to the secondary side of LH Δ, the difference between the current transformer secondary circuit of the current flowing into phase. To both sides of the transformer secondary circuit current flows in opposite phase difference in the Y / Δ-11 wiring side of the current transformer transformer Δ LH \\ if the press into Y/Y-12, then the Y connection transformer current transformer devices to be connected as LH Y / Δ-5. Shown in Figure 5, into the difference between the current transformer circuit current LH IA2 = IB2 \\ a IA2\\ , does not consider the case of CT angle error, IB2 \\ and IB-phase, IA2\\ and IA with the corresponding, (IB a IA) phasor points 5 points for Y / Δ-5 wiring, the phasor diagram shown in Figure 6 (a). Current transformer LH \\ into the loop current Ia2 difference in phase with the Ia, point to 11 points, so Ia2 and IA2 reversed, if the values ??are equal, the current loop into the difference is zero, the phasor diagram shown in Figure 6,

Easy to determine the method used, as long as the assumptions connected with three-phase symmetrical sides of purely resistive load, the voltage and current in phase relationship to current and voltage phasor diagram, phase of the same name (such as the A-phase) of the phase voltage of phase relationship, it is easy a few minutes to determine the wiring. This method to determine the three-phase transformer or current transformer connection group with practical and simplicity.