Skip to main content

Sequence voltages, currents and powers (2071)

Short answer

Compute symmetrical components via phase-A reference and a=1∠120°. V0=83.53∠148.61° V, I0=6.44∠165.0° A, S0=1548-j455 VA; V1=178.38∠113.56° V, I1=7.54∠99.31° A, S1=3911+j993 VA; V2=36.55∠-26.82° V, I2=4.28∠-106.55° A, S2=84+j462 VA. Total S = 5542.6 + j1000 VA.

A 3-phase supply system has following voltages VA = 220∠120° V, VB = 120∠30° V and VC = 240∠210° V and the currents are IA = 10∠150° A, IB = 5∠0° A and IC = 15∠180° A. Determine sequence currents, voltages and powers.

Sequence components (phase A reference, sequence A-B-C, a=1∠120∘a = 1\angle120^\circ): X0=13(XA+XB+XC)X_0 = \frac13(X_A+X_B+X_C), X1=13(XA+aXB+a2XC)X_1 = \frac13(X_A+aX_B+a^2X_C), X2=13(XA+a2XB+aXC)X_2 = \frac13(X_A+a^2X_B+aX_C); sequence power Sk=3VkIk∗S_k = 3V_kI_k^*.

Sequence voltages

V0=13(220∠120∘+120∠30∘+240∠210∘)=−71.31+j43.51=83.53∠148.61∘ VV1=13(220∠120∘+120∠150∘+240∠90∘)=−71.31+j163.51=178.38∠113.56∘ VV2=13(220∠120∘+120∠270∘+240∠330∘)=32.62−j16.49=36.55∠−26.82∘ V\begin{aligned} V_0 &= \tfrac13(220\angle120^\circ + 120\angle30^\circ + 240\angle210^\circ) = -71.31 + j43.51 = 83.53\angle148.61^\circ\ \text{V} \\ V_1 &= \tfrac13(220\angle120^\circ + 120\angle150^\circ + 240\angle90^\circ) = -71.31 + j163.51 = 178.38\angle113.56^\circ\ \text{V} \\ V_2 &= \tfrac13(220\angle120^\circ + 120\angle270^\circ + 240\angle330^\circ) = 32.62 - j16.49 = 36.55\angle{-26.82^\circ}\ \text{V} \end{aligned}

Sequence currents

I0=13(10∠150∘+5∠0∘+15∠180∘)=−6.220+j1.667=6.440∠165.0∘ AI1=13(10∠150∘+5∠120∘+15∠60∘)=−1.220+j7.440=7.540∠99.31∘ AI2=13(10∠150∘+5∠240∘+15∠300∘)=−1.220−j4.107=4.284∠−106.55∘ A\begin{aligned} I_0 &= \tfrac13(10\angle150^\circ + 5\angle0^\circ + 15\angle180^\circ) = -6.220 + j1.667 = 6.440\angle165.0^\circ\ \text{A} \\ I_1 &= \tfrac13(10\angle150^\circ + 5\angle120^\circ + 15\angle60^\circ) = -1.220 + j7.440 = 7.540\angle99.31^\circ\ \text{A} \\ I_2 &= \tfrac13(10\angle150^\circ + 5\angle240^\circ + 15\angle300^\circ) = -1.220 - j4.107 = 4.284\angle{-106.55^\circ}\ \text{A} \end{aligned}

Sequence powers

S0=3V0I0∗=3(83.53∠148.61∘)(6.440∠−165.0∘)=1548.2−j455.3 VAS1=3V1I1∗=3(178.38∠113.56∘)(7.540∠−99.31∘)=3910.6+j993.1 VAS2=3V2I2∗=3(36.55∠−26.82∘)(4.284∠106.55∘)=83.8+j462.2 VA\begin{aligned} S_0 &= 3V_0I_0^* = 3(83.53\angle148.61^\circ)(6.440\angle{-165.0^\circ}) = 1548.2 - j455.3\ \text{VA} \\ S_1 &= 3V_1I_1^* = 3(178.38\angle113.56^\circ)(7.540\angle{-99.31^\circ}) = 3910.6 + j993.1\ \text{VA} \\ S_2 &= 3V_2I_2^* = 3(36.55\angle{-26.82^\circ})(4.284\angle106.55^\circ) = 83.8 + j462.2\ \text{VA} \end{aligned}
SequenceV (V)I (A)P (W)Q (var)
Zero83.53∠148.61°6.440∠165.0°1548.2−455.3
Positive178.38∠113.56°7.540∠99.31°3910.6993.1
Negative36.55∠−26.82°4.284∠−106.55°83.8462.2
Total5542.61000.0

Check

S=VAIA∗+VBIB∗+VCIC∗=2200∠−30∘+600∠30∘+3600∠30∘=5542.6+j1000S = V_AI_A^* + V_BI_B^* + V_CI_C^* = 2200\angle{-30^\circ} + 600\angle30^\circ + 3600\angle30^\circ = 5542.6 + j1000 VA ✓

Answer: S0=1548−j455S_0 = 1548 - j455 VA, S1=3911+j993S_1 = 3911 + j993 VA, S2=84+j462S_2 = 84 + j462 VA; total S=5542.6+j1000S = 5542.6 + j1000 VA.

✓ Answer checked by Claude Sonnet 5.5

All Power System Analysis II chapter 4 questions →