ABB Power Services

Our aim is to increase systems reliability and extend the life of their equipment with concomitant gains for our customers’ competitiveness. We support our customers with high-quality services in preventive and corrective maintenance to improve risk mitigation and improved safety. ABB's service portfolio allows utilities and industrials to maximizing the return on all assets by ensuring a high reliability, reducing life cycle costs and ensuring optimized performance while lowering environmental impact.

Friday, October 26, 2012

Avoid Two Common Reasons for Circuit Breaker Failure This Winter – How to Check your Tank and Mechanism Heaters

Power mechanism performance is affected by several factors. The greatest risk factor to your high voltage circuit breaker mechanism is the same risk your vehicle is facing now – cold weather.  While ABB continues to produce workhorse mechanisms, we often compare them to a diesel engine. 

Even the most powerful and efficient engines on the market must stay warm in the winter to start on time, every time.  For your switchgear to trip on time, every time, you can’t simply plug in the combustion chamber then crank the mechanism again until 51% of the phases will arc.  Your switchgear’s mechanism must continuously stay above the manufacturer’s required ambient temperature to ensure consistent, reliable, and safe performance.  All three phases must operate synchronously to avoid a failure or loss of power. 

Fall is operationally the best time to check your mechanism heater. Loads on your fleet are reduced as air conditioning is turned off and children have returned to school. 

Checking your mechanism heater is easy:

With the A/C circuit energized, check the total heater circuit current using a clamp-on amp meter or with the A/C circuit de-energized, check the total resistance using an Ohm meter. Reference your wiring diagrams for expected results. Be sure to wear all necessary PPE (personal protective equipment).

It is just as important to check your tank heaters.  Why?  If the tank heater runs at temperatures above the set parameters it will burn out the heating elements eventually.  Or, if it does not turn on, as the temperature drops some of the SF6 will change from a gas to liquid and pool on the bottom of the tank.  This will cause the pressure on the remaining gas to drop, decreasing dielectric strength and lead to a failure.  

The tank heaters should not be on at this time. To test to the tank heaters, clamp an amp meter to the heater A/C power source and turn the on setting to above the current temperature. You should hear the heater contactor click on. Once it does, measure the wattage. Divide the wattage by voltage = current value.  This should match your drawings.

Another benefit of checking your heaters now is preventing nuisance alarms and related unnecessary costs to investigate those false alarms.

In summary, now is the best time for preparing your high voltage switchgear for a long, cold winter.  It is imperative to check your mechanism heater and tank heater using the steps outlined above.  Don’t get left out in the cold!  Contact ABB HV Service (724-696-1300) if you have questions or need support.

No comments:

Post a Comment