Page 523 - Handbook of Electrical Engineering

514 HANDBOOK OF ELECTRICAL ENGINEERING

RMU Ring main unit.
ROM Read only memory.
RTD Resistance temperature detector.
RTU Remote transmitter unit.
Rx Receiver.
S

S Apparent power in volt-amperes.
s or p Laplace operator in mathematics, for transfer functions.
S Slip of a rotating machine with respect to 1.0 pu.
SBM Single buoy mooring.
SC or S/C Short circuit.
SCADA Supervisory control and data acquisition system.
SCF Standard cubic feet of a gas.
SDR Single discipline review.
SECT Skin effect current trace heating.
SELV Safety extra-low voltage.
SF6 Sulphur hexafluoride.
SI Syst` eme Internationale d’Unit´ es
SLI Double-ended, linear arc tube.
SOLAS Safety of life at sea, a document relating to marine practice.
SON Diffused ellipsoidal outer bulb, single-ended lamp.
SON-T Clear tubular outer bulb, single-ended lamp.
SON-TD or – L Clear tubular outer bulb, double-ended lamp.
SON-R SON lamp, with internal reflector.
SOL CU Solid copper.
SOX U-shaped arc tube, single-ended lamp.
Sox Sulphur based gas emissions.
SP Single phase.
sq Square, e.g. sq mm is square millimetres.
sq2 Square root of 2.0 = 1.414214
sq3 Square root of 3.0 = 1.732051
SSR Synchronisation check protection relay.
STG Steam turbine generator.
STR CU Stranded copper.
SWA Steel wire armour.
SWBD Switchboard.
SWGR Switchgear.
SYNC or Sync Synchronising.
T

T or t Time, usually in seconds.
Td Time constant in seconds for the quantity ‘d’.
TDRM Time delayed restart relay.