Maintenance, Monitoring & Strengthening of Substation Grounding – Experience of GETCO

In a recent global scenario, rapid load growth, technological advancement and raised living standards has emphasized power utilities to provide reliable, uninterrupted and quality power supply to the end consumers. Efficient and Effective Grounding system plays important role in keeping uninterrupted and reliable power with increasing fault levels of substations. Earthing is also of prime importance as it directly deals with human safety. Gujarat Energy Transmission Corporation Ltd. (GETCO) operates around 2000 EHV substations across the state, has taken many initiatives towards improvement of grounding system across its network in a way to fulfil the commitment to deliver quality power supply. This paper will delineate mainly three distinguished Grounding enhancement practices for effective strengthening, maintenance and monitoring of the earthing system of GETCO network.

(a) Adoption of Maintenance Free Treated Earthing: To mitigate the maintenance challenges of conventional Cast Iron Pipe type earthing and to improve its life, GETCO has started installing Maintenance Free Earth pits at all EHV substations since 2014. The paper describes in detail the technical specification and drawing adopted for maintenance free earthing and modality of execution as per site condition. The acceptance criteria for ground enhancement material through tests like leaching, sulphur detection, corrosion and resistivity tests, is also discussed in detail.

(b) The Earthing Adequacy Study (EAS): This study was carried out in GETCO for 14 nos. of critical substations of more than 50 years old where earthing has considerably got weakened. The purpose for performing this EAS is to access the entire switchyard grounding for its healthiness. Moreover, to ensure efficient and unambiguous earthing installations at all upcoming EHV substations, GETCO has made the Earthing Adequacy study mandatory since the year 2015. In this paper, the parameters attribute and methodology to conduct EAS in accordance with standards and to levy necessary stitching of weak earthing areas based on derived parameter is explained.

(c) Strengthening of earthing of specially designed Load Shedding Transformers (LST), which is a special drive being done for more than 4600 nos. of 11kV agriculture feeders across the Gujarat state. This paper reports the special grounding scheme derived for earthing the LST phase wire that draws continuous current even during normal operating condition. The assessment for pre and post earthing installation and the result testified for earthing parameters is discussed.

By implementing effective earthing measures through adoption of various Grounding Enhancement practices, GETCO have witnessed several benefits like improved availability of transmission network, reduced nos. of interruptions and safe operating scenario which have marked significant impact on system operation.