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Annunciation System

Guidelines and consideration in planning and designing annunciation system for

grid stations

1. Audio and visual signalsEvery power system should be provided with an annunciation system both

audio and visual signals in the event of trouble or abnormal conditions.

a. Audio signals. Horns and intermittent gongs are used for audible signalsdevises. An intermittent gongs is provided in the grid control rooms.

Howler horn are used in the unit area and areas where back ground

noise is high or area remote from yards.

b.

Visual signals. These are provided lighted lettered window panels ofannunciatar. In larger grid stations annuciator panels indication is

augmented by unit trouble lamps located in a readily visible position

close to the unit. The event recorder is normally located in the control

rooms. Separate annunciators (when provided ) for station service

system and switchyards should be located on associated control panels

of the station service switchgear or on the switchyard control panels.

2. Annunciatorsa. General. The annunciators system should be designed for operation on

ungrounded 110VDC or 220VDC.All remote contacts used for trouble

annunciation should be electrically independent of contacts used for

other purpose so annuciator circuits are separated from DC circuits .

Auxiliary relays should be provided where independent contacts

otherwise be obtained. The annunciator equipment should use solid

state logic units, lighted window or LED type, designed and tested for

surge with standing capacity in accordance with IEC.

b. The switchboard annunciator operational sequence should be manual orautomatic.

Automatic reset should be employed when there is either an SER or

SCADA system backup. When system is controlled and dispatched by

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through the SCADA system , the reset features of the annuciators

should be coordinated to ensure proper operation.

Switchboard Annuciator operational sequence

Field

contact

Control pushbutton

or switch

Alarm

light

Horn Aux or repeater

contact

Normal Off Off Off

Abnormal Flashing On On

Abnormal Acknowledge or

silence

On Off On

Normal Reset Off Off Off

Normal test On Off Off

Certain alarm points have several trouble contacts in parallel byequipment group .generally, these are transformer bucholz and

pressure relief valve operation.

A control console window-indicating light annuciator is common to all

units. One unit at time can be selected by use of the appropriate unit

trouble status lighted pushbutton. Visual indication is provided when

the unit switchboard annuciator is activated . The console window

indicating lights are generally grouped by switch board annuciator

points and provide essential trouble status to the operator. Unit trouble

are normally categorized by shutdown, differential, over current,

cooling. The window indicating light annuciator provides back up for a

sequential event recorder. Unit switchboard annuciator remote control

switches to silence and reset the switch-board annuciator should be

provided on control console.

Signal Description Signal Description

87t Transformer diff 21 Line distance

74 T/F over heat 50G T/F neutral o/c50/51T T/F o/c 49 T/F over heat

86 BF lock out 42 Cooling failure

71Q T/F low oil 63Q T/F sudden pressure

94L1 Line lock out 63 Loss of CB energy for

trip and close

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