Table of Content

Introduction1

Discussion1

Does Plant Require a Fire Protection System?2

CO2 Suffocates Fires2

Water Spray Douses Fires2

Pre-action systems3

Water Mist Smothers Fires3

Clean Agent Gases Are Now Available4

Consider a Hybrid Suppression System4

Fire Detectors4

Automatic or Manual Release5

The consequence of an inadvertent system discharge6

Types of Sprinkler Heads7

Works Cited8

Fire Protection Features

Introduction

Fire protection systems for air-cooled hydroelectric generators have several special requirements due to these generators' peculiar geometries. This survey of options will help plant owners and operators make the best equipment selections for their plants and thereby avoid unexpected surprises. The global hydroelectric industry is very busy relicensing and modernizing existing facilities. In the U.S., hydroelectric generating station modernizations are multi-year projects that either upgrade or replace all the powerhouse systems, including the fire protection systems. Generator fires are a low-likelihood event, but their consequence, in the absence of fixed fire protection, can be the complete destruction of the generator or warping of the stator and rotor ' frames from heat exposure.

Discussion

The fire risk associated with non-hydroelectric air-cooled generators in the electric utility industry is low, and fixed fire protection systems are usually unnecessary. However, the geometry of the typical hydroelectric generator provides larger surface areas that increase fire spread. Combustible materials in the generator -- such as end turn insulation, winding insulation, end shields, cable, and contamination (such as dust and/ or oil particles) -- can also quickly increase the spread of a fire.

Does Plant Require a Fire Protection System?

One of the difficult engineering decisions during a modernization project is deciding whether or not to provide a fixed fire protection system. As with numerous engineering questions, the answer is: "It depends."

Equipment selection depends on a number of factors, such as the size of the machine, the winding insulation, and the risk tolerance of the stakeholders (including owners, operators, insurers, and financial institutions). It also entails considering the consequences of extended unit downtime, such as replacement power purchases, if the unit damaged by fire.

From a fire hazard standpoint, there are essentially two types of air-cooled generator winding insulation: thermoplastic and thermoset. In the end, a determination that fire protection needed will probably be driven more by the potential for huge monetary losses during a lengthy forced outage than by physical damage to the generator alone.

CO2 Suffocates Fires

Although carbon dioxide (CO2) is a very effective agent, the fire extinguishing success of CO2 systems requires enclosure integrity and the proper application rate of the gas. CO2 systems extinguish fires by starving them of oxygen, so a release of the gas into an enclosed space poses a risk to humans.

Water Spray Douses Fires

Water spray systems are the second-most-common fire protection system, assuming that an adequate water supply is available, because, like CO2 systems, water spray systems engineered using common components and water is abundant at hydroelectric plants, spray systems are also the least expensive for air-cooled generators.

Water is a highly effective fire extinguishing agent, but the generator should be de-energized prior to, the application of water -- a disadvantage compared with CO2 systems. Water spray systems extinguish fire by direct cooling, ...