Substations convert our energy from hundreds of thousands of volts to manageable levels. Once transformed, energy can be safely channeled along cables to our homes and places of work. A substation demands the seamless interaction between its components, notably transformers, circuit breakers and protective relays--a failure in even one element may lead to grid collapse. Testing the elements of a substation is an essential practice engineers conduct numerous times over a substation’s operating lifespan, and can be generally divided into the following phases.
Phases of Substation Testing
- Factory Acceptance Tests (FATs)
Factory acceptance tests occur pre-installation, and verify that the components created for the substation meet design and function requirements before delivery and integration into the system. Adhering to the supplier/buyer contract is paramount to the success of acceptance testing; these tests, after all, are intended to confirm to the buyer that the components are crafted correctly.
Commissioning is the next round of testing the electrical parts will undergo before service. Manufacturer data will be cross-checked, products will be looked over for transportation damages and wiring will be replaced in refurbishment projects. Existing parts with shorter lifespans will be renewed while others remain, and the interaction between old and new parts will be assessed.
- Maintenance Tests
Maintenance testing is conducting annually or once every three years as part of an overall substation inspection, and along with electrical tests includes a thorough cleaning, substation inspection, wire replacement and troubleshooting. Site Acceptance Tests (SATs) will be performed as a kind of initial maintenance testing, evaluating the electrical compatibility of the parts in a system, this time on a live grid.
3 Essential Tests for Substation Components
A transformer converts a high input to a lower output, transforming a primary current into a secondary current of an appropriate power level for residential and commercial buildings. Transformer testing verifies the controlled metering of a transformer in accordance with standards like ANSI.
Circuit breakers, or switchgear, safely switch off currents to prevent shortages and outages. Circuit breaker testing assesses factors like the resistance and timing. A circuit breaker should achieve minimum possible energy loss when inactive and be checked for corrosion or oxidation, as well as adherence to IEEE C37 and IEC 62271.
A protective relay detects minor fluctuations in voltage, resistance, current or temperature and trips the circuit breaker in response. Relay testing will prove relay logic functions are working “as set,” and meet the requirements of ANSI C37.90, IEC255-4, IEC60255-3, and IAC standards, among others.