DC Systems and Station Light & Power (SL&P) Review

This flashcard set covers the components, voltage thresholds, operational procedures, and troubleshooting steps for DC systems and Station Light & Power (SL&P) within a substation environment.

DC System Components

The four parts consisting of batteries, battery charger, DC ground detector, and DC distribution panel.

Ground Detector

The specific component of a DC system that may or may not exist at certain substations.

Battery Usage Rationale

Batteries are used instead of the charger to ensure the station can sustain itself for at least $12\,hours$ because the battery charger is not considered reliable.

Float Voltage ($60\,cell$ battery)

The state when cells are at $2.25\,V$ each, totaling $135\,V$.

Nominal Voltage ($60\,cell$ battery)

Occurs at $2\,V$ per cell ($120\,V$ total), indicating the charger has been lost and should be reported.

Solid Station

A condition where battery voltage has depleted below a level where the station will operate, occurring at $1.75\,V$ per cell ($105\,V$ for a $60\,cell$ station).

Solid Sub ($24\,cell$ battery)

A station that would show $42\,V$ as its depleted operating limit.

Battery Longevity Methods

Actions to extend life include unscrewing control lights, de-energizing non-critical DC buses, and not turning on emergency lights.

Charger Return to Service

The sequence of turning on AC, waiting $30\,sec$, then turning on DC.

Charger Removal from Service

The sequence of switching from AC to DC without a required $30\,sec$ wait.

COLA Circuit C1

The circuit used to close.

COLA Circuit C2

The circuit used to operate.

COLA Circuit C3

The circuit used for light indications.

COLA Circuit C4

The circuit used for alarms.

DC Alarm Conditions

The five conditions are loss of DC, abnormally high voltage, abnormally low voltage, loss of battery charger (loss of AC), and ground detector activity.

Battery Issue Contacts

The TSO (Transmission System Operator) should be contacted first, followed by the battery shop.

Critical DC Buses

Includes DC operating, DC relay, LBFB, EMS, CB control circuit, back up relay, electronic relay, and control bus.

Loss of Control Bus

Means the breaker (CB) cannot be operated remotely and must be operated from the relay itself.

DC Ground Troubleshooting Order

The TSO will direct the de-energization of non-critical buses first; backup protection must never be removed.

HMI (Human Machine Interface)

The screen (often top right corner) where battery voltage can be checked if the physical charger screen is damaged at a SAS station.

SL&P Fuse Disc De-energization

The procedure of opening the center phase first, followed by the outside phases.

SL&P Fuse Disc Re-energization

The procedure of closing the outside phases first, then closing the center phase last.

Battery Duration Calculation

Based on Bulletin 7 in SSI: divide amp hours by load amps (current/normal amps).

AC Critical Loads

Four critical loads for station light and power: battery charger, bank fans, air conditioning for electronic relays, and heaters/fans/compressors in CBs.

SL&P Testing Group Setting

Settings at a SAS station should be left on 'primary' to prevent increasing the minimum trip and losing the ground relay.