Automatic Transfer Switch - Power

 

What is Automatic Transfer Switch?

The Automatic Transfer Switch (ATS) is a critical piece of equipment that alternates the origin or the source of power, typically between your utility power and backup/emergency power, ensuring your system’s ability to stay online. It is inherently important in making sure that this part of your emergency system is working properly. Also, because this particular part of your system is usually relatively complicated in nature, they are rarely examined or tested after the ATS has left its manufacturing facility. This is precisely why Industrial Tests, Inc. should be your first choice in ATS testing, so that you and your facility can feel safe and confident in its ability to transfer power, in the event of losing normal power. Automatic Transfer switch tests, tests utility power or standby generator power—and conducts the power to critical loads. 

https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=110

NFPA 110, the standard for emergency and standby power supply systems, states “the monthly test of a transfer switch shall consist of electrically operating the transfer switch from the standard position to the alternate position and then a return to the standard position”. The standard also requires a monthly generator run. The best way to perform both these tests is by operating the test toggle on the ATS when the generator isn’t running, and confirming that the ATS properly signals the generator to start and run before transferring building load.

How Does an Automatic Transfer Switch Work?

An automatic transfer switch, or ATS switch, connects your standby generator to your home. Normally, electricity flows from the utility to your home's main electrical panel, where it powers all your circuits.

Automatic transfer switches act as the "brain" of your entire electrical system. Once installed, they can automatically switch between electricity coming from your utility and generator power.

When the transfer switch detects a power outage, it switches your home to generator power. Afterward, it detects when the power is restored and switches your home back to utility power.

Why Automatic Transfer Switch Testing is Done?

Many critical electrical systems are not being maintained to the proper standard, and some are not maintained at all. Why? Maybe it’s because electrical systems and components are being installed improperly. Maybe it’s because of poor system design that leaves little access. Or maybe it’s because many facility engineers still regard maintenance as a necessary evil. In order to evaluate the cost of maintenance, one must factor in the cost of lost service due to an unplanned failure plus the cost of replacement.

The automatic transfer switch (ATS) is a critical system component of the emergency power system, and proper maintenance of an ATS depends on the type of switch and its position in the critical power infrastructure. It is essential to find out whether your ATS is within manufacturers specifications during a planned examination, so that you don’t run the risk of finding this out during an unforeseen outage and you are unable to switch your system to its secondary power. Intermittent testing of your ATS is the sure-handed method of guaranteeing that your emergency system is as reliable as it can be.

TRANSFER SWITCH PROTECTS LINEMAN

The utility line voltage is normally "stepped down" before entering the building, by a transformer. The transformer can work in reverse when voltage is sent through it in the opposite direction and "step up" the voltage. This stepped up voltage, back-feeding through the utility lines, may electrocute workers that come into contact with the utility lines.

Protects Linemen

  A Properly Installed Transfer Switch Protects  Linemen

A TRANSFER SWITCH PROTECTS THE HOME

Improper connections can allow electrical current from the generator to short circuit with utility line current when power is restored. This can cause a fire in the electrical system.

 Protects The Home or Business

  A Properly Installed Transfer Switch Protects Your Home or Business

A TRANSFER SWITCH PROTECTS THE GENERATOR\

Improper connections can allow electrical current from the generator to short circuit with utility line current when power is restored. This could cause the generator to explode or burn.

     Protects The Generator

  A Properly Installed Transfer Switch  Protects  Your Generator

The Three Primary Reasons for the Monthly Test

1. A test is an active demonstration that the EPSS is still able to function as intended. If a switch is going to fail to transfer, it’s better to have the switch fail while connected to a live normal source during a test than to have it remain connected to a dead normal source during an actual power outage.
2. An automatic transfer switch is an electromechanical device with moving parts. Like the pistons and crankshaft in an automotive engine, the moving parts in an ATS can seize if they’re left in one position for months or years. Regular exercise will help ensure that moving parts will continue to operate smoothly.
3. A transfer switch test transfers building load onto the generator for the duration of the generator test. Most standby power generators of more than 100kW are diesel engine driven, and all major diesel generator manufacturers recommend a load of at least 50% of maximum capacity during monthly generator tests. NFPA requires the same thing, for the simple reason that running under a light load is very bad for a diesel engine.

Running a diesel generator in an unloaded condition—with no ATS transfer, thus with no building load connected—causes carbon buildup in the cylinders and exhaust system, a condition known as “wet stacking.” This problem reduces efficiency and power, and in extreme cases it can cause an exhaust system to catch fire. To reduce a wet-stack condition once it has developed, some facility owners will rent a resistive load bank and connect it to the standby generator for a full-load run of sufficient duration to “burn out” the build-up. The cost for such an exercise is substantial, and the relief provided is only temporary.

What is Done During an Automatic Transfer Switch Test?

Following steps are performed

1. Simulate loss of normal power.
2. Return to normal power.
3. Simulate loss of emergency power.
4. Simulate all forms of single-phase conditions.

ATS Checks Include

• Check wiring and connections are tight with no discolouration of metal, melted plastic and odour indicating excessive heat.
• Verify external operating mechanism is clean and re lubricate if found dirty.
• Check for any deterioration of wiring insulation such as cuts and abrasions. Replace or repair any damaged wiring.
• Check tightness of wiring connections. Retighten to specification if any loose wiring found.
• Perform insulation resistance tests on all control wiring with respect to ground.
• Perform a contact/pole-resistance test.
• Verify settings and operation of control devices.
• Calibrate and set all relays and timers.
• Verify phase rotation, phasing, and synchronised operation as required by the application. .
• Check ATS main power switching contacts condition. Clean or replace. Replace contractor assembly if necessary.
• Exercise the generator set under load.
• Test the transfer switch’s automatic control system.
• Test all indicators (LEDs) and all remote control systems for operation.
• Inspect the outside of the transfer switch for any indication of wear, excessive vibration, leakage, high temperature, contamination or other deterioration.
• Verify all external components are in place, firm, tightened and not excessively worn.
• Inspect the inside of the transfer switch for any indication of excessive vibration, leakage, high temperature, contamination or any other deterioration.
• Verify all internal components are in place, firm, tightened and not excessively worn.

Remove the ATS from panel and test