A robust voltage unbalance allocation methodology based on the IEC/TR 61000-3-13 guidelines

The International Electrotechnical Commission (IEC) has introduced approaches for managing continuous power quality disturbances (harmonics, flicker and voltage unbalance) in power systems through the allocation of emission limits to customer installations, which are based on a common philosophy. However, it has been found that these harmonics and flicker allocation methods lead to planning levels being exceeded even when no customer exceeds the allocated emission limit. Subsequently, an alternative allocation policy which is referred to as the dasiaconstraint bus voltagepsila (CBV) method has been developed to overcome this problem. This paper examines the application of the recently introduced IEC voltage unbalance allocation procedure (IEC/TR 61000-3-13) which involves an additional aspect ie. the emission arising from system inherent asymmetries. Paper identifies that this voltage unbalance allocation method also leads to a problem similar to above employing a simple 3-bus test system. A new voltage unbalance allocation policy based on the CBV method is suggested. It is demonstrated that this new voltage unbalance allocation technique satisfies the key allocation objective of complying with the set planning levels.