ESTADOS FINANCIEROS CONSOLIDADOS
Nota 36 Operaciones con Partes Relacionadas
The Ebla LV three phase distribution system voltage has been selected as 400 V. The LV loads to be fed from each substation has been classified as Utility Loads, Process Loads and Emergency Loads and accordingly each of the Plants has been provided with a Utility Switchboard, Process Switchboard and an Emergency Switchboard.
The incomer details and the rating of these switchboards at GGS are as follows:
o The 400V Utility MCC (323-MCC-1-1) is fed by two incoming lines, feeders from two nos. 11/0.420 kV, 2500 kVA distribution transformers (i.e., 323-TML-1-1A and 323-TML-1-1B). The switchboard consists of two incomers and a bus-coupler and various outgoing motor feeders and bulk power feeders. The rating of the switchboard is 4000 A, 400 V, 3 Phase + Neutral, 4 Wire, 50 Hz, 80 kA for 1 sec.
o The 400 V Process MCC (323-MCC-1-3) is fed by two incoming feeder from two nos. 11/0.420 kV, 1600 kVA distribution transformers (i.e. 323- TML-1-3A and 323-TML-1-3B). The switchboard consists of two incomers
and a bus coupler and various outgoing motor feeders, heater feeders and bulk power feeders. The rating of the switchboard is 2500 A, 400 V, 3 Phase + Neutral, 4 Wire, 50 Hz, 50 kA for 1 sec.
o
The 400 V Emergency MCC (323-MCC-1-2) is fed by two incoming feeders, one from the 400 V Utility MCC (323-MCC-1-1) and second from 1200 kW Emergency DG Set. The rating of the switchboard is 3000 A, 400 V, 3 Phase + Neutral, 4 Wire, 50 Hz, 80 kA for 1 sec.The LV switchboards are totally enclosed, metal clad, free standing, double front semi- draw-out type with ACBs for incomers and bus-couplers and MCCB/SFU for outgoing motor/bulk power feeders.
The LV normal switchboards are rated to carry the full load current of one of its feeding power transformer. The short circuit ratings of the switchboard and impedance value of the power transformer have been adequately selected for isolated operation of two power transformers connected to the switchboard. The emergency switchboard is rated to cater to the connected emergency loads.
The PMS shall carry out the following control and status-monitoring functions with respect to the LV switchboard:
o Closing/opening of all LV incoming, bus coupler, outgoing ACB feeders. o Closing/opening of all LV motor breakers, heater feeders without
Thyristor Control Panels based on the command from ICSS.
o Measurement of all important electrical system parameters including: a) Ampere, kW, frequency of the LV switchboard incomer
b) Ampere, Bus Voltage, Bus Frequency for LV Bus Tie
c) Ampere, Bus Voltage, Bus Frequency for outgoing ACB feeders
d) kW for Motor Feeders and Heater feeders without Thyristor Control Panels 1.Monitoring of the fault status from the output of intelligent relays provided in
the LV switchboard.
2.Recording and reporting of Sequence of Events (SOE) of feeders including motor feeders and Incomer Feeders following a trip.
3.Transmitting of all outgoing motor feeder contactor and fault status (as required) to the ICSS
Control supply for the switchboard incomer, bus coupler & outgoing breaker feeders is derived from the respective substation 110 V DC UPS panel.
Interlocks
Interlock between incomer and bus-coupler breakers to ensure Two-Out of Three breakers remain closed at any point of time, with provision to defeat the interlock during momentary paralleling of incomers.
Slow bus transfer scheme/Auto change over scheme along with momentary paralleling scheme between incomers and bus coupler breaker of utility & process MCC has been provided for transfer of power from one incomer to other during failure of power to any one of the supplies.
Distribution Boards for Lighting, HVAC, Heat Tracing & Cathodic Protection
Separate conventional type distribution boards will cater to the power requirement for lighting and small power system, HVAC system, Heat Tracing System and Cathodic Protection System. The above distribution boards shall be controlled from the switchboard only.
400 V/230 V AC UPS System
Two numbers of 50 Hz, equally rated, physically & electrically separate UPS systems each with its own battery is provided in the substation to cater to each of the following loads (which includes DCS and PMS power supplies):
(a) Individual Instrument load supplies – 400V, 3 Phase UPS (b) Telecommunication load supplies – 230V, 1 Phase UPS
The UPS units will operate independently for supplying power to the load. The neutral of each of the UPS system is solidly earthed. The rating of the Instrument Supplies AC UPS is 60 kVA (GGS) each with UPS battery backup duration of 6 hours. The rating of the Telecom AC UPS is 4 kVA with UPS battery backup duration of 8 hours.
Incoming supply to the UPS is provided from the Emergency MCC and the bypass supply provided from normal switchboard. Static Switches in the UPS ensure uninterrupted and synchronized switchover from UPS supply to bypass in the event of mains failure or inverter/rectifier failure of UPS.
The 230 V AC UPS supply for telecom loads is distributed to the loads through
conventional 230 V, 50 Hz, 1 phase distribution boards with MCCB incomer feeders and MCB outgoing feeders.
The 230 V AC UPS supply for Instrumentation loads is derived from 400 V, 50 Hz, 3 phase distribution boards with MCCB as incomer feeders and MCCB outgoing feeders. The 400 V and 230 V AC UPS distribution boards are located at the substation. Provision of receiving redundant UPS supply is made in all critical loads.