Power

Power Transmission

Substation fires can be catastrophic. Fires in substations can severely impact the supply of power to customers and the utility company’s revenue and assets. These fires can also create a fire hazard to utility personnel, emergency personnel, and the general public. Hence, Fire Protection is a critical and indispensable requirement in the construction and maintenance of a substation.

The recognition of fire hazards and consideration of adequate fire protection measures are some of the key considerations for the design and operation of new or existing substations.

Particular Fire Risks to Substations:

Types and causes of fires that can occur in substations

The types of fires depend on the equipment and systems used in the station. Fires involving dc valves, outdoor or indoor oil insulated equipment, oil insulated cable, hydrogen cooled synchronous condensers or PCB insulated equipment are usually well documented and these types of equipment are easily recognized as a fire hazard.

There are a number of other substation specific types of fire that are not as well documented.

Energised electrical cables with combustible insulation and jacketing can be a major hazard because they are a combination of fuel supply and ignition source. A cable failure can result in sufficient heat to ignite the cable insulation which could continue to burn and produce high heat and large quantities of toxic smoke. Oil insulated cables are an even greater hazard, since the oil increases the fuel load and spill potential.

The hazard created by mineral oil insulated equipment such as transformers, reactors and circuit breakers is that the oil is a significant fuel supply that can be ignited by an electrical failure within the equipment. Infiltration of water, failure of core insulation, exterior fault currents, and tap-changer failures are some of the causes of internal arcing within the mineral insulating oil that can result in fire.

This arcing can produce breakdown gases such as acetylene and hydrogen.

Depending on the type of failure and its severity, the gases can build up sufficient pressure to cause the external shell of the transformer tank or ceramic bushings to fail or rupture. Once the tank or bushing fails, there is a strong likelihood that a fire or explosion will occur.

A possible explosion could cause blast damage.

The resulting oil spill fire could spread to form a large pool of fire depending on the volume of oil spill containment, slope of surrounding area and the hype of surrounding ground cover (i.e. gravel or soil) Thermal radiation and convective heating from the oil spill fire can also damage surrounding structures and structures above the fire area.

Substations are exposed to the common industrial fire hazards such as the use and storage of flammable compressed gases, hot work, storage and handling of flammable liquid, refuse storage, presence of heating equipment and storage of dangerous goods. The local fire codes or NFPA codes can provide assistance in recognizing common fire hazards.

Switchyard Hazards

Some of the specific components encountered in substation switchyards that are fire hazards are:

The failure of some of the critical components such as transformers and breakers can directly result in losses of revenue or assets.

Other switchyard components could create a fire exposure hazard to critical operational components i.e. combustible service buildings located close to bus support structures or transmission lines.

Control and Relay Building Hazards

A control or relay building can include the following potential hazards:

A fire in any of these components could damage or destroy critical control or protection equipment. Damages could result in long outage to customers as well as significant revenue losses.

Indoor Station Hazards

Fires in indoor stations are caused by some of the same substation related hazards as switchyards and control rooms. The impact of any fire involving oil insulated equipment, oil insulated cable and HVDC (high voltage dc) valves in an indoor station can result in major fires with accompanying large asset losses and service disruptions. The basic problem with major fires in indoor stations is that the building will contain the blast pressure, heat and smoke which can result in:

The basic problem with major fires in indoor stations is that the building will contain the blast pressure, heat and smoke which can result in:

Areas/EquipmentsTo Be Protected:

Kind of Protection Required: