Switchgear is a complex apparatus composed of various moving and fixed parts and contacts, including conductor, circuit breaker, switches, fuses, and relays, serving as a critical component of the power protection system responsible for protecting other components on the electrical grid from damaging fault currents. Its core function is to provide conductivity under normal conditions while performing fault isolations when fault occurs.
These devices, consisting of a control house and multiple circuit breakers, serve as the primary means for rerouting power through the various branches of distribution circuits. They provide overcurrent protection against through faults, which provides a means for circuit interruption when these overcurrent conditions are present.
This is accomplished through a switchgear’s ability to effectively isolate sections of the electrical system when excessive current levels are detected. Switchgear also serves as a means for safely rerouting power without disrupting supply to the end user.
Despite the critical role these devices have on overall safety and reliability, mechanical or dielectric failure can commonly occur. This is due in part to the basic design of the equipment causing thorough offline testing and visual inspections to be costly and labor-intensive tasks.
Challenges of Offline Testing
Offline maintenance of switchgear can be a difficult task and is a time-consuming process, which is why asset management requires online real-time monitoring. Offline testing requires racking out of breakers which exposes rear contacts to excessive wear and possible misalignment. More importantly, the crew who performs the testing could be susceptible to potential arc flash hazards. With offline testing, slow interrupting times can often go undetected due to operation of the breaker before testing. The incipient stages of insulation failure can also often go undetected.
Offline switchgear maintenance, while essential for ensuring the safety and reliability of electrical systems, presents several challenges. These difficulties can impact the efficiency of the maintenance process, the safety of personnel, and the overall reliability of the power system. Here are some of the key challenges associated with offline switchgear maintenance:
1. System Downtime
Offline maintenance causes interruptions to operations as well as production halts. Offline maintenance requires the switchgear to be de-energized, leading to interruptions in industrial processes, commercial activities, and power supply to critical infrastructure.
The resulting downtime can lead to significant financial losses, especially in industries where continuous operation is crucial, such as manufacturing, data centers, and hospitals.
2. Safety Concerns
Utilities can present a high-risk environment with a number of electrical hazards. Maintenance personnel face significant risks when working on de-energized switchgear, including the potential for accidental re-energization or exposure to stored energy in the system.
3. Resource Intensive
Offline maintenance requires skilled and experienced personnel to perform the tasks safely and effectively. Recruiting and retaining such personnel can be challenging, and continually performing offline testing requires labor commitment that could be better spent elsewhere.
Convenience of Online Monitoring
Online switchgear monitoring is an easy, comprehensive approach to managing switchgear. With online monitoring, asset managers have a viable test of breaker operations every time the breaker operates. Monitoring allows for direct maintenance on the breakers that need it. Monitoring also offers a comprehensive look at breaker operations and bus Partial Discharge activities.
Dynamic Ratings’ Smart Capture technology allows for condition based monitoring of switchgear devices, capturing waveform signatures as they relate to the operation of the trip and close coils during breaker operations. Through analysis of these captures, a great deal of information concerning the switchgear’s performance can be learned, and the unit can monitor up to six bays of switchgear using a single monitoring system.
Our switchgear monitor captures small changes in switchgear performance allowing problems to be detected well before failure occurs.
Switchgear Monitor (SWGM)
Dynamic Ratings Switchgear Monitor (SWGM) has a waveform overlay that allows for an intuitive and easy-to-interpret visual diagnosis of performance degradation in switchgear mechanics. By comparing the waveform signature with memorized reference waveform, deviations are visually represented and can direct maintenance crews to the problem of performance degradation.
Our SWGM monitors the motor starts, current, and runtimes. It watches for heater insulation deterioration due to moisture ingress. It observes the bus, particularly for PD as a leading indicator of insulation breakdown. The SWGM also provides real-time pressure readings for GIS breakers and operational bus, forecasting leakage rates, and providing a mass gas loss for reporting. Finally, it keeps an eye on the cable in the gear itself as well as the feeder cable.
The SWGM Prevents Unintended Outages
Industry data shows that switchgear has one of the industry’s highest failure rates, creating a need for inspection and continuous monitoring. Unlike insulation systems used in motors and generators, the insulation systems in switchgear are not resistant to insulation deterioration caused by partial discharges. During switchgear failure, the outage is usually for an extended period. On older equipment, spare parts are limited and many times custom manufacturing is required, adding to the outage time.
Without monitoring, equipment operators must rely on cyclic maintenance and offline testing to determine switchgear conditions. The ability to properly maintain switchgear through time-based maintenance is becoming less effective because of aging infrastructure, decreasing operating budgets and a decline in specialists.
Continuous monitoring provides peace of mind and helps to extend the life of your switchgear.
Partial Discharge Detection
The switchgear monitor configuration may also be combined with Dynamic Ratings SCM to provide partial discharge monitoring of the switchgear bus and connectors, allowing tracking or faulty connections to be detected.
The Switchgear and Cable Monitor (SCM) continually monitors partial discharge (PD), and stores and correlates operating dynamics. The SCM provides information on the health of the medium voltage insulation systems of switchgear, cables, bus duct and unit substations.
Adding Dynamic Ratings’ partial discharge monitoring to your switchgear monitoring system will detect corona present from the breakdown of insulating system loose connections and surface tracking that may be a result of contaminants or moisture.
Cable Monitoring
90% of cable failures occur at splices and terminations. As these accessories break down, they generally produce partial discharges prior to failure. In order to monitor cables, the SCM takes data from radio frequency current transformers (RFCTs) that are placed around the cable termination shields. If the shields are ungrounded, then a GPCS sensor is used. The condition of the cable, type of insulation, and type of shield construction will determine how far one can ‘see’ down the cable.
Condition Based Maintenance with the Switchgear Monitor
Because routine maintenance requires that switchgear is operated and de-energized, performance degradation issues are often masked by exercising the mechanics of the switchgear. This may prevent crews from truly understanding the state of the equipment between maintenance schedules. The maintenance itself is extremely invasive and often leads to the introduction of new problems that were not previously present.
The Switchgear Monitor Provides Easy to Interpret Data
Our waveform overlay allows for an intuitive and easy-to-interpret visual diagnosis of performance degradation in switchgear mechanics. By comparing the waveform signature with memorized reference waveform, deviations are visually apparent and can direct maintenance crews to the problem of performance degradation.
Variations in the waveform capture are easily associated with the mechanical performance of the switchgear’s various parts, which allows many operational deficiencies to be detected in their earlier stages, providing detailed data concerning the diagnosis of these problems.
How it Works
Let’s take a look at how it works.
As the switchgear is called on to perform a trip operation, the current begins to flow in the trip circuit through the 52a auxiliary contact and the plunger begins to be pulled through the coil, which is then observed in the waveform as the current starts to rise on the waveform graph.
Once the plunger has achieved maximum velocity, the current will reach a peak point and begin to fall. This decrease will continue until the plunger strikes the latch releasing stored energy, allowing the switch gear to begin to open, which is visible in the waveform capture as a momentary rise in current immediately followed by the current continuing its downward trend.
The switchgear monitor captures this waveform and uses it as a baseline fingerprint for normal operation, which provides a reference for comparison of future trip operations and allows for a detailed diagnosis of any variations of breaker performance.
If something looks out of place, an alarm will notify the user of the problem. This information allows utilities to optimize maintenance plans and performance of their assets, while adapting to changing system requirements.
Get In Touch to Learn More
Switchgear is a key asset in the reliability of the power supply, and monitoring is easy to implement if you work with the right specialists. Switchgear monitoring along with enterprise asset management software through Dynamic Ratings increases reliability, efficiency, and safety in the workplace.
If you want to collect data on your substation assets to reduce the risk of unexpected failure and increase situational awareness, while evaluating the equipment in your substation (transformers, circuit breakers, switchgear, and more), all the while measuring their performance to make sure everything is working properly, contact our experts today to learn more.
Author: Tyler Willis, Dynamic Ratings