Fault location method for petal-shaped distribution network with inverter-interfaced distributed generators

In this paper,a fault location method for the petal-shaped distribution network(PSDN)with inverter-interfaced distributed generators(IIDGs)is proposed to shorten the time of manual inspection.In order to calculate the fault position,the closed-loop structure of the PSDN is skillfully exploited,and the common control strategies of IIDGs are considered.For asymmetrical faults,a fault line identification formula based on the negative-sequence current phase differences is presented,and a fault location formula only utilizing the negative-sequence current amplitudes is derived to calculated the fault position.For symmetrical faults,the positive-sequence current at both ends of lines and the current output from IIDGs are used to identify the fault line,and the positive-sequence current on multiple lines are used to pinpoint the fault position.In this method,corresponding current phasors are separated into amplitudes and phases to satisfy the limitation of communication level.The simulation results show that the error is generally less than 1%,and the accuracy of the proposed method is not affected by the fault type,fault position,fault resistance,load current,and the IIDG penetration.

A d-axis based current differential protection scheme for an active distribution network

The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu-tion network,in a way which can severely influence protection.This paper proposes a d-axis-based current differential protection scheme.The d-axis current characteristics of inverter-interfaced distributed generators and synchronous generators are analyzed.The differential protection criterion using sampling values of the d-axis current component is then constructed.Compared to conventional phase-based current differential protection,the proposed protection reduces the number of required communication channels,and is suitable for distribution networks with inverter-interfaced distributed generators with complex fault characteristics.Finally,a 10 kV active distribution network model is built in the PSCAD platform and protection prototypes are developed in RTDS.Superior sensitivity and fast speed are verified by simulation and RTDS-based tests.

Pilot Protection Based on Amplitude Comparison for Renewable Power Teed Lines

Fault behaviors of inverter-interfaced renewable energy generators(IIREGs)are quite diverse from those of synchronous generators(SGs).They show the variable system impedance,the limited current and low inertia,so the proportional brake differential protection installed on the transmission line has a high risk of failure for phase-phase failures.To cope with this adaptive problem,a new pilot protection is proposed considering the huge differences in both current amplitudes.Also,an improved criterion is presented for a scenario with a teed line.The existing protection principles focus excessively on the fault current characteristics of IIREGs,so they cannot operate correctly once IIREGs do not output their fault current.This happens when IIREGs produce no power or the circuit breakers exactly reclose on permanent failures.However,the proposed method has good performance for the above cases.The proposed method only requires current amplitude information,and in this case the strict synchronizing measurement is not necessary.Case studies are performed under different fault conditions,and they confirm the proposed method has good performance under different fault conditions.Furthermore,it is also verified using field-testing data.