FIRE FIGHTING SYSTEM FOR INDOOR POWER TRANSFORMERS - substation

  FIRE FIGHTING SYSTEM FOR INDOOR POWER TRANSFORMERS 

SCOPE

This specification mainly covers the design, manufacturing, testing, delivery, communication and guarantee for fire fighting systems for Indoor power transformers

 

    Any material not specifically mentioned in this specification or not shown on the drawing but required for proper performance and operation shall be furnished install.

DEFINITIONS

The fire detection system of transformers

 Heat detector and smoke detection:

 Rate of rising, fixed temperature detectors and ionized smoke detectors shall provide a double knock detection system.

CLASSIFICATION

            Fire fighting for indoor power transformers covered by this specification shall be

by using carbon dioxide CO2 as an extinguishing agent the system shall have its own local control and alarm panels.

REQUIREMENTS

           

   Environmental Conditions

            The environmental conditions listed  in the table 1 shall apply:-

Table (1) Standard Environmental Conditions

 

Clause	Description		Value
1-	Pressure MB-annual means.		1013
2-	Atmospheric Temperature °C:- Maximum mean daily Minimum mean daily Yearly mean		47* -5 30
3-	Relative humidity % Maximum relative humidity Minimum relative humidity Average relative humidity Daily mean		100 20 75 95
4-	Rainfall mean-annual total (mm)		65
5-	Maximum wind speed (m/sec.) at 10m above ground level.		35
6-	Soil temperature at a depth of 1.5 m.		25°C
7-	Solar energy radiation W/m²		>1100
8-	Wind pressure N/m²		766
9-	Absolute black bulb °C max. recorded		75.7
10-	Thunderstorms		Occasional
11-	Sand storms	Occur occasionally especially in desert.
12-	Pollution	Heavy pollution >50 mS
13-	Seismic load	According to the Egyptian Code and attached map.

 

Note:             This table is valid altitude (0-1000m)

            Maximum temperature shall be in accordance with substation location in Egypt.

         For Cairo Zone.

 

 DESIGN

 

       To prevent or reduce fire in case of oil spill, transformer oil collection pits shall be provided.

        Indoor transformer station shall be equipped with efficient fire detection and extinguishing system.

Fire detection System

 -         The detection systems in transformers shall instantaneously come into action in case of a fire isolating the transformer by tripping the transformers circuit breakers from both sides and put a fire extinguishing system into action.

 -         The number of detectors shall be suitable for the transformer and mounted at the cover level of the transformer. The detectors shall detect any amount of abnormal temperature rise and smoke generated by a fire on transformer tank, or the terminals or even on the transformers bed.

 -         The detectors shall be designed and equalized such that they do not operate at slow temperature rise which may occur due to variation of load, ventilation, solar effect…etc and shall ensure complete security such that it will not be operated due to any reason except fire.

 -         The detectors of each type shall be connected in series by a fire-resistance cable which is connected to detection unit and the detectors shall be simple, study inspects vibration proof and moisture acid-resistant construction.

1)     A double detection system shall be designed in order to prevent the activation of the extinguishing system due to false indication.

 2) To minimize the possibility of inadvertent gas release caused by spurious alarms, the CO₂ system shall be automatically initiated by a “double-knock” smoke/heat detection system.

 3)  Provision shall be made for a guard current flowing through the detectors. Interruption of the guard current due to the breaking of the elements series connecting cable or load terminal shall activate an audible and visible alarm signal at the detection unit of the equipment indicating interruption of guard current. This alarm signal must not activate the extinguishing system and the signal can be used for blocking the extinguishing system if needed.

Fire Extinguishing System for Indoor Power Transformers

 

Fire fighting system for indoor transformers shall be mainly designed in accordance with codes/ standards In order to distinguish the fire in the shortest possible time, the system shall conform to the following technical requirements :-

             Application of carbon dioxide on total flooding units.

 -         The system shall include carbon dioxide storage bottles/tank fully charged, cylinder valve, refrigeration unit if required and discharge heads, mounting brackets, automatic and manual release controls, piping and nozzles, and safety monitors.

 -         The carbon dioxide bottles/tank shall be housed in a suitable room or enclosure located near the point of usage. Space shall also accommodate the spare bottles foreseen.

 -         The system shall be complete with the required high-pressure manifolds, discharge nozzles, safety lock-off devices and visual indicators showing whether the system is charged locked-off or discharged.

 -         There shall be a time delay of 10 seconds between initiation of alarm signal and discharge.

-         If the carbon dioxide is stored in rechargeable cylinders under high pressure, the cylinders shall have a safety rupture disc at each manifold and a capacity of 45 kg each and a suitable working pressure.

-         The carbon dioxide system pipe work shall be galvanized and tested for 150 percent of the working pressure.

-         A CO2 release should stop oil pumps, fans, and close doors dampers.

 -         A trolley or trailer shall be supplied for moving carbon dioxide bottles about the site.

 -         Weighting devices shall be provided for each carbon dioxide cylinder to allow accurate assessment of the contents of the cylinders. The cylinder shall be weight in the vertical position.

 -         A common fire alarm control the panel should be provided containing sets of extinguishing release modules, one for each transformer.

 Function

 The agent would  be stored as a liquid in pressurized containers and a fixed pipework system would transport the agent to suitably located discharge nozzles.

 The CO₂ the system would be automatically initiated by the double detection system combination of heat and smoke detectors. The manual release would be available from a break glass unit located adjacent to each transformer enclosure or mechanically at the  CO₂ cylinder bank.

 A common CO₂ cylinder bank would be provided together with “pilot” cylinders and automatic selector valves to direct the CO₂ into the appropriate transformer enclosure.

 Control Panel

 A common fire the alarm control panel will be placed in a lockable cabinet containing sets of extinguishing release modules, one for each transformer enclosure.

 A signal from the automatic fire detection system shall be  received by the fire alarm control panel, which in run shall initiate an electric actuator on the  “pilot tank valve, thereby applying pressure to the pneumatic actuators on the CO₂ tank valves and automatic selector valves, thus releasing the extinguishing agent into the pipework and discharge nozzle system. Simultaneously the fire the alarm control panel shall operate the alarm sounders in the appropriate area.

TESTING AND INSPECTION

 

If the supplier has carried out type tests on the offered equipment in the last ten years according to the relevant standard then the supplier shall provide type test certificates for the approval of the owner, otherwise type tests have to be carried out in the presence of the owner.

ACCEPTANCE AND REJECTION

 

The supplier shall forward to the purchaser, two copies of certificate proving that all tests required have been carried out and also samples & catalogs of the equipment used.

SPARE PARTS

 

            List of manufacturer’s recommended spare parts shall be included in addition to spare parts requested by the purchaser if required

GUARANTEE

             The supplier shall guarantee fire fighting equipment against design, material, and manufacturing defects for a period as given in tender documents.

 SUBMITTALS

 

      The submittals shall include the following:-

 -         Reference list of all the components of the system.

 -         Description of fire extinguishing system for indoor transformers.

 -         Fully detailed type test reports.

 -         Fully detailed of routine tests to which all units will be tested before dispatch.

 -         Others which are required by purchaser.

     The following documentation shall be provided:-

 -         Detailed dimensional drawings.

-         Detailed mounting drawings.

-         Detailed wiring diagrams.

-         Maintenance instructions.

-         Copies of design test certificates where available.

-         Factory test certificates.

 

 DELIVERY

 

The manufacture shall be responsible for and shall repair or replace at his own expense any and all damaged equipment where damage was due to improper preparation for supply.

 

 REFERENCE LIST

  

            The tenderer shall submit a reference the list that the proposed equipment has been in successful operation in an integrated system on three different substations of same or higher capacity outside country of the manufacturer and/or in EEHC network for a period not less then three years during the last ten years.

 

The experience of the manufacturer and the sub-manufacturer shall be evaluated on the above basis.