Electricity + Control November 2018

DRIVES + MOTORS + SWITCHGEAR

Suiting up for switchgear Planning ahead to understand and prevent failures

Gabriel Paoletti, Eaton

Switchgear is a critical part of every utility's power distribution system; and, as such, any malfunction can be catastrophic. Utilities can take these power system compo- nents for granted, mistakenly believing that the switchgear will continue to run with- out any attention or maintenance.

Take Note!

1. Prior to beginning switch- gear maintenance tasks, utilities should complete a required arc flash study. 2. Additionally, all circuit breakers and electrical switching devices should be labelled. 3. The facility should also have an up-to-date elec- trical single line diagram. 1 3 2

S witchgear malfunctions can, however, spell immediate disaster in several ways. One concern is with the time required to repair or replace the switchgear following a fail- ure. Downtime from outages can be extensive. A switchgear assembly contains the copper bus, connections and control wiring of the individual circuit breakers. So while a spare can replace an individual circuit breaker in 30 minutes, it can take weeks to repair or replace the entire switchgear assembly. A switchgear failure can also prevent power flow completely. Should a switchgear malfunction cause damage to the outgoing or incoming cables that are connected, this damage can result in ad- ditional equipment, labour and, most importantly, additional time to repair or replace. This article explores some common causes of switchgear malfunctions and provides recommen- dations on the core preventative measures utili- ties can take to avoid unexpected setbacks from equipment failure. To avoid downtime, these basic steps must always be addressed before exploring or investing in any new maintenance automation technologies. Attend to environmental conditions Through a recent analysis of IEEE reported fail- ure data and customer surveys, it was discovered that preventable causes account for over 50% of all switchgear failures. These findings were first summarised in the paper, Past, Present and Fu- ture Maintenance Practices: Monitoring of Elec- trical Equipment Failure Indicators and Alarming , presented at the 2015 IEEE IAS Pulp and Paper Industry Committee Technical Conference in Mil- waukee, Wisconsin.

The most common switchgear failures can be split into three general categories that are all environ- mental in nature: 1. Humidity and internal arcing. 2. Dust and surface contamination. 3. Mismanaged heating resulting from either overloaded equipment or deteriorated connec- tion points or electrical contact areas. The good news is that implementing a simple maintenance program can control all these com- mon causes. A few additional causes, such as a lightning strike, operator error or rodent damage, might seem unavoidable. But these also can sometimes be ad- dressed beforehand by routine maintenance. For example, monthly inspections would help ensure that no unexpected openings exist in which rodents could enter the location to destroy the switchgear. Regular switchgear testing and inspection can go a long way. For some tasks, it's important to en- sure that factory trained or independently certified individuals complete the switchgear maintenance. Quality vendors typically provide these services and can advise on a plan specific to the site. For some tasks, it is important to ensure that factory trained or independently certified individu- als complete the switchgear maintenance. Prior to beginning switchgear maintenance tasks, utilities should complete a required arc flash study and label all circuit breakers and electrical switching devices. Next, the facility should have an up-to-date electrical single line diagram. Without these two items, the operation, maintenance and Safety checks, preplanning for switchgear maintenance

Personnel safety must always be considered and prioritised.

4 Electricity + Control

NOVEMBER 2018