This is part 4 in a series on staged fault testing.
Staged fault testing is vital to grid reliability, especially as the fourth generation electric energy grid is established. This next generation grid will have more renewable sources adding more distributed energy than ever before; it will experience expanded electric vehicle usage, which increases demand for energy; and it will face the risks of wide area blackouts from more heat waves, wildfires, and other severe weather events linked to climate change.
To ensure that new lines on the grid are prepared for energization, confirm that existing lines are modelled and protected correctly, and enhance grid reliability, electric utilities need to perform staged fault testing.
This article outlines the cost and schedule impacts of performing a staged fault test on 230 KV open air transmission lines. The equipment necessary for staged fault testing will be a worthwhile investment for utilities, as it can be used repeatedly. Follow along to learn more.
230 KV Staged Fault Equipment
Two trailer loads of equipment will be needed to perform staged fault tests. One low boy trailer will transport a 230 KV motor operated air break (MOAB) switch and other parts to the staged fault test site. This trailer will not exceed height or weight limits on most highways.
A double drop, low boy trailer will transport a 230 KV, SF6, dead tank circuit breaker to the staged fault test site. This trailer will likely exceed height limits and require the use of oversize load placards and pilot cars.
The 230 KV, SF6, dead tank circuit breaker will be a spring close / spring open circuit breaker that opens immediately upon closing. The main power contacts should remain closed for at least 16 milliseconds, but less than 50 milliseconds, every time the circuit breaker is closed. This circuit breaker will clear the staged fault whether or not the circuit breakers associated with the 230 KV transmission line operate as designed.
Other equipment is discussed in more detail in our prior article, Staged Fault Testing: Equipment and Procedures.
Cost and Schedule of a Staged Fault Test
The costs and schedule associated with staged fault testing can be split into three phases: set up, perform, and disconnect. Cost impacts are tabulated in person-hours assuming inefficiencies and eight-hour days. Let’s take a closer look at the three phases of staged fault testing.
1. Set Up Staged Fault Equipment: 4 Days
Installation of equipment necessary to perform a staged fault test will take four days. Required equipment includes a temporary circuit breaker equipped with motor operated air break switches, drops from three single phase stirrups, and grounds.
Setup activities can be completed with no impact to the critical path schedule. Costs can be estimated using the hours listed below.
2. Perform Staged Fault Test: 1 Day
After the equipment is installed, the staged fault crew must receive authorization to perform the staged fault test. Each staged fault test should take a three-person crew only 3 hours to perform. Two tests can be performed during an 8-hour workday: one three phase fault and one single phase fault.
Testing activities will impact the critical path schedule. Costs can be estimated using the hours listed below.
3. Disconnect and Remove Equipment Post-Test: 3 Days
Disconnection of staged fault test equipment from a 230 KV transmission line should require less than four hours. Removal of a temporary circuit breaker and transportation to a storage facility will take several days.
Removal activities can be completed with no impact to the critical path schedule. Costs can be estimated using the hours listed below.
1 Day of Testing, Decades of Improved Grid Reliability
Installing a new 230 KV circuit breaker and completing routine test activities requires weeks of work when foundations, grounding, control cables, etc. are required. Within this time, one day is needed to perform staged fault testing.
If the goal is to reduce the number of protective relay misoperations to less than 1% per year, the choice is clear. Perform staged fault testing before new transmission lines are accepted for service or explain snafus when lightning strikes a line, a four bolt connector opens and a phase conductor drops, or any other failure occurs.