Wind speed varies continuously throughout a day resulting in fluctuating wind farm output power. When such a farm is connected to the grid through a line, the transmitted power and the relay end voltage (with respect to grid voltage) fluctuate continuously. In this paper, the protection of such a line with distance relay is investigated. The ideal trip characteristic for distance relay is studied with change in conditions of the wind farm. A method is proposed to set the boundary adaptively using local information only

Adaptive Distance Relay Setting for Lines Connecting Wind Farms

The fault resistance introduces an error in the fault distance estimate, and hence may create an unreliable operation of a distance relay. A new compensation method based on fault resistance calculation is presented. The fault resistance calculation is based on monitoring the active power at the relay point. The compensated fault impedance measures accurately the impedance between the relay location and the fault point. The relay has shown satisfactory performances under various fault conditions especially for the ground faults with high fault resistance. This new compensation method avoids the under-reach problem in ground distance relays

Ground distance relay Compensation based on fault resistance calculation

A novel adaptive current protection scheme for distribution systems with distributed generation

When a transmission line close to points of common coupling (PCCs) experiences a short-circuit (SC) fault, the fast reactive power control of voltage-source converter-HVDC (VSC-HVDC) is likely to affect the protective relay operation of transmission lines. To study the performance of distance relays on an ac grid with an offshore wind HVDC network, this paper presents an apparent impedance calculation method, which utilizes the bus impedance matrix (Zbus) to calculate the impedances viewed by distance relays during a three-phase SC fault. The proposed method is used to identify the potential miscoordinated Zone 2 relays in the proposed combined ac/dc system. The analysis is verified by software simulation results. It is shown that the proposed method results in accurate impedances viewed by distance relays. It also identifies the protective device settings on the ac grid that need to be adjusted due to HVDC control of offshore wind generators.

Distance Protection of AC Grid With HVDC-Connected Offshore Wind Generators

Optimal coordination of distance and over-current relays in series compensated systems based on MAPSO

This paper presents a method for calculating zone-2 setting of distance relays without causing coordination problems. The proposed method is based on the impedance seen by distance relays when faults are simulated on the reach of zone-1 of primary relays for the maximum and minimum generation outputs of the power system. It is shown that the proposed method increases the reach of zone-2 relays without causing coordination problems. The proposed method is modified for use in an adaptive protection system. It is shown that further improvements can be achieved when settings are calculated using the proposed method and the prevailing system conditions. Measures to alleviate the impact of communication failure are discussed. The proposed method and its adaptive version were applied to an existing power system and some results are reported in the paper.

R.M. Palomino

Papers

A new approach for calculating zone-2 setting of distance relays and its use in an adaptive protection system