Investigation of Spark Gap Role in Protection of Distribution Transformer Against Lightning Surges Using ATP-EMT

Abstract

This research implores the capability of the commonly used surge protection device, spark gap, for the protection of distribution transformer in an event of transient over-voltage surge. The spark gap is one of the most valuable protection components because it is small in size, strongly made and capable of withstanding rough handling, has minimal capacitance, and possess the ability to carry transient currents of the order of kiloamperes. However, in some occurrences the spark gaps can be slow to conduct the transient current. This paper investigates the time lag characteristics of the spark gap with respect to the increasing time front of the transient surge. The protective device is installed with a distribution transformer of an 11kV line and the line is energized with a transient source at an adequate distance, and the timely response of the device, for different cases, is recorded with the help of ATP-EMTP (Alternative Transient Program-Electromagnetic Transients Program) simulations. The distribution transformer is faced with transient surges of different parameters, within suitable range, to completely asses the ability of the device to guarantee an effective protection to the distribution. The research aims to lead to an increase in the reliability and performance of the existing spark gap models, and ensure better protection of the distribution transformers. LESCO (Lahore Electric Supply Company) was approached for data regarding the 11kV transmission line for an urban area of Pakistan. The research has been performed on a 630, 11/0.415 kV, distribution transformer installed on 11kV line.