CIGRE 2005 Joint Meeting 1 CH, Gino Bacchini & Walter Baass CIGRE SC B5 Colloquium in Calgary 2005: SR for PS#3 Question 14 Joint Meeting and Colloquium of the CIGRE’ Study Committee B5 - Protection & Automation and IEEE Power System Relaying Committee Question #14: What influences of shunt capacitor banks on protection measurement are reported and how are the effects mitigated ?

CIGRE 2005 Joint Meeting 2 CH, Gino Bacchini & Walter Baass ACRE-RONDONIA Power System Shunt Capacitor Banks 188 km 302 km Weak Infeed Strong Infeed

CIGRE 2005 Joint Meeting 3 CH, Gino Bacchini & Walter Baass Thevènin Reduction of the ELN Acre-Rondonia System for Computer-Aided Analysis & Simulations Porto Velho S/S Abuna S/S Rio Branco S/S E2E2  Z S2, Z S20  Z S1, Z S10 E1E1 302 km A2A2 A1A1 L1 C1C1 C2C2 L2 188 km Weak Infeed Strong Infeed Shunt Capacitor Banks Shunt Capacitor Bank 160 MVAr 130 MVAr 20 MVAr

CIGRE 2005 Joint Meeting 4 CH, Gino Bacchini & Walter Baass The problems Shunt capacitors have a considerable impact on the circulating currents and transient behaviour of the protection relay during line faults under weak infeed conditions. Some faults can challenge the basic principles and, unless measures are taken, incorrect operation of the protection devices can result. Some examples of such conditions are close-up faults where the faulted voltage is virtually zero, so that the correct direction is more difficult to determine. Reverse faults in Porto Velho S/S may be seen as a forward fault when one side of the transmission system is weak. Moreover, the apparent fault resistance depends on the fault location and is very pronounced in Abuna S/S (Semaphore effect). This has a similar effect as an additional strong infeed, and thereby increases enormously the measured fault resistance when the fault location approaches the opposite line-end near Porto Velho S/S.

CIGRE 2005 Joint Meeting 5 CH, Gino Bacchini & Walter Baass Directional Characteristics of Distance Protection F1F1 E2E2  Z S2, Z S20 Z L1, Z L0  Z S1, Z S10 E1E1 I1I1 F2F2 I2I2 F3F3 F3F3 F1F1 F2F2 Fault trajectory is crossing the tripping area

CIGRE 2005 Joint Meeting 6 CH, Gino Bacchini & Walter Baass Adapted Directional Characteristics for Acre-Rondonia Power System F2F2 E2E2  Z S2, Z S20 Z L1, Z L0  Z S1, Z S10 E1E1 I1I1 I2I2 Enough room available for the fault trajectory excursion in the backward direction Fault trajectory is crossing the tripping area F2F2 F2F2 X R -X -R-RRX/8 RR/2 -RRE RRE/2 ZS 7° / 14°  0 HEST V For Ph-Ph & 3Ph Loop

CIGRE 2005 Joint Meeting 7 CH, Gino Bacchini & Walter Baass Conclusions In geographically large countries, the power must often be transferred from remote power generation centres to the load centres. In the case presented, the transmission system angle can therefore exceed 60°. For the majority of faults, distance protection operates correctly in the Acre-Rondonia system. To achieve the best results under all system conditions, more than one polarisation quantity for the directional decision must be used: - directional decision built-in each of the 6 measured loops - directional decision based on more than one polarising quantity (adaptive measurement characteristics with automatic selection) - directional decision using cross-polarising healthy phases in conjunction with memory polarisation, selectivity conditions and filtering techniques.