TRANSFORMER BAY FIRE PROTECTION

WHAT IS A TRANSFORMER BAY?


The word "bay" when related to transformers is used to describe a closed or open cubicle where electrical equipment is placed. Some small bays sometimes contain a water filter or control gear. There are open or closed bays for power distribution and motor starters etcetera, often called "panels".

Due to the potential for fire with large oil cooled transformers, what would normally have been an open “bay” containing a transformer is now being built as closed bays, often with fire suppression systems of some form, so as any potential fire can be contained and extinguished within the building.

There can be open-air bays, like those you see in a switchyard. There, you find transformer bays, breaker bays, incoming and outgoing bays where transmission lines "land" and "start". 

In substation parlance it usually describes a circuit breaker with its associated disconnectors, instrument transformers, protection equipment and earth switches. A substation would normally be comprised of a number of such bays.

WHY AND HOW PRESSURE RELIEF IS USED IN TRANSFORMER BAYS?


The AFP Air Tech Ltd range of pressure relief and blast vents have been specifically designed and tested to vent the excess pressure in a building that can arise when an electrical fault in a transformer gas or oil cooled compartment causes a discharge into the surrounding building.

AFP have been working very closely with UK Power Networks UKPN in the UK to create the venting standards for all of the UK's major transformer installations. AFP's testing has not only provided UKPN with a 'live discharge' based study of the effects of a potential over-pressure from a transformer fault, but also helped reduce the amount of blast venting required.

AFP BLAST SIMULATOR

There is no standard or testing protocol for blast venting in these exact circumstances and this is why AFP has built its Blast Simulator to mimic these types of extremely rapid pressure discharges and design our own testing standard for blast vents.
AFP Blast Simulator
AFP Blast Simulator SHX-UN
The AFP Blast Simulator consists of a 1.8m3 10 bar variable volume pressure cylinder that discharges into a 20ft steel container via 150mm diameter pipe with a bespoke instant blow off valve. The diameter of the blow off valve orifice can be sized to suit any rupture disk diameter or pressure relief valve and the volume of the pressure cylinder can be changed to suit the transformer oil or gas cooled compartment.

This produces an instant pressure discharge such as that produced by a transformer fault. Typically these types of discharges last between 0.1 and 0.2 seconds. When the correct sized AFP SHX-UN Pressure Vents are installed, this results in the time to peak pressure, in the building, being suppressed to just 0.06 seconds which has the effect of massively reducing any potential overpressure that could result in structural damage.
By monitoring the pressure in the pressure cylinder, the test container and also the position of the blast vent blades at 20HZ, the relationship between the rate of gas volume increase in the test container, verses the rate at which the blast vent blades open, can be associated with peak pressure in the container.

DISCHARGE TIME 0.1S

9. LH Graph P2

PEAK PRESSURE 0.06S

10. RH Graph P2
The data collected from the AFP Live Discharge Tests can also be integrated into the results produced by certain software simulations. Most of the simulations AFP have seen do not take into account the rate at which the blast vent opens, in the 0.01s increments needed to fully assess how the over pressure relates to the free vent area of the vents over time. This now means that thanks to AFP blast testing, the theoretical simulations can finally be matched to an expected discharge from the 'real world'.

SHX-UN BLAST VENTS

SHX-UN
The SHX-UN Pressure Vents come in two forms for transformer building protection, SHX-UN Pressure Vents and SHX-UN MOT motorised. The motorised being able to motor open for ventilation purposes.

SHX-UN BLAST VENTS ADDITIONAL TESTING


The SHX-UN Pressure Vents range has also been Gas Ignition explosion tested. Using a high speed camera they have been measured to fully open in 11ms with no structural failures at non vented enclosure test pressure of up to 20 bar (oxygen/acetylene mix)
Explosion flame sequence

CERTIFIED FIRE TESTED TO 4 HOURS FOR ALL SIZES

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ENVIRONMENT TESTING OF ALL OF OUR EXTERNAL LOUVRE UNITS, WHICH HAVE BEEN PROVEN TO GIVE SUPERB EXTERNAL WEATHER PROTECTION

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