AUXILIARY SERVICES OF STATION SCRN 3G/6CT-03 TECHNICAL FEATURES

GENERAL

3x460V, 60Hz voltages for auxiliary services, 110V, 60Hz voltages for usual lighting and 24VDC for safety lighting within the drilling plant are provided through the auxiliary services supply electric equipment.

This equipment comprises:

- three-phase automatic switches QTA1, QTA2 for supplying auxiliary services transformers with voltage from the 600 VAC bar system;

- 2 auxiliary services transformers TTA1 and TTA2;   - 2 general bar systems 3 x 460V (Bus "A" and Bus "B") that might be interconnected through a longitudinal couple;

- the general null bar (bus "N");

- the PE general bar (bus "PE");

- auxiliary electric set supply;

ELECTRIC EQUIPMENT FOR SUPPLYING AUXILIARY SERVICES

The station disposes of two 600/460/110V transformers for supplying auxiliary services with 3 x 460V and 3 x 110V voltage, respectively. Both of these have star-connected secondary with the neutral connected to the general null bar.

Transformers denoted TTA1 and TTA2, respectively, have the following rating data:

- apparent rated output 450kVA

- primary rated voltage 600V

- primary rated current 433A

- secondary 1 rated power 400kVA

- secondary 1 rated voltage 460V

- secondary 1 rated current 502A

- secondary 2 rated power 50kVA

- secondary 2 rated voltage 110V

- secondary 2 rated current 262A

- rated frequency 60Hz

- secondary 1 connections group Dyn - 11

- secondary 2 connection group Dyn - 11

- insulation class H

The two transformers are of dry type and all three windings are fitted with temperature probes connected to two monitoring relays TH1 and TH2 mounted in cabinet D2J. Relays have three temperature thresholds set as follows:

- at 40șC temperature the command to start transformers cooling fans is issued;

- at 100 șC temperature - taken for the alarming threshold - a contact is shut down on one of the programmable automated device entries displaying the alarm signal;

- at 135 șC temperature - taken for the failure threshold - opening of switches F1 and/or H1 in transformers secondary is ordered;

Transformers are supplied from the 600V bar system by means of two automatic plug-in switches QTA1, QTA2, places in cabinets 10 and 11 of the 600V voltage distribution (D10I and D11I).

The tri-pole plug-in Sentron WLI 800 N switches are manually actuated and are fitted with ETU 25B control unit and have the following technical parameters:

- rated current   800A

- rated voltage  690V

- rated frequency  50/60Hz

- insulation voltage  1000V

The ETU25B control unit allows signalization of failures, long-standing overload release, delayed short-lasting overload release as well as instantaneous short-circuit release.

Adjustment is developed in steps, set values being the following:

- I_r 0.7I_n (560A)

- I_sd 1.25I_n (1000A)

- t_sd 0.2 s

Transformer TA1 supplies the general 3 x 460V (bus "A") bar system by means of switch D1J.F1, while transformer TA2 supplies the general 3 x 400V (bus "B") bar system by means of switch D2J.H1. Switches F1 and H1 are plug-in, tri-pole, type IZMB1-V800, manually actuated, fitted with XZMV control unit and have the following technical parameters:

- rated current 800A

- rated voltage 690V

- rated frequency 50/60Hz

- insulation voltage 1000V

The XZMV control unit allows signalization of failures, long-standing overload release and delayed short-lasting overload release.

Adjustment is done in steps, set values being the following:

- I_r 0.7I_n (560A

- I_sd 4I_n (3200A)

- t_sd 0.2s

The two general bar systems Bus "A" and Bus "B" are inter-connectable by means of the longitudinal couple D2J.G1. This is done using a three-pole, plug-in, manually actuated IZMB1-V800-type switch, with the following technical features:

- rated current 800A

- rated voltage 690V

- rated frequency 50/60Hz

- insulation voltage 1000V

In order to provide electric power to auxiliary consumers until startup of the 1500 kVA groups, an electrical set is used with a maximum power of 390 kVA for a voltage of 460V, connected to the general bar system Bus "B" by means of switch D5J.J1. This is a three-pole, plug-in, manually actuated, NZM3-type switch, fitted with a control unit.

Technical features of J1 switch are as follows:

- rated current 630A

- rated voltage 690V

- rated frequency 50/60Hz

- insulation voltage 1000V

Its control unit has the following adjustment values:

- I_r 0.9I_n (567A)

- t_r 10s

- I_sd 4I_n (2520A)

- t_sd 500ms

- I_i 8I_n (5040A)

All four switches QTT1,QTT2,G1 and J1 are equipped with MN 110 VAC minimum voltage coils connected for excluding any in parallel connection of two supply sources. Five supply versions for the general 3 x 460V bar systems could be developed, by coupling the switches as shown in the table below:

 

The potential of closing shutting down the switches, converted in supplying the minimum voltage coils, is signaled by the message "OK" displayed on switches.

Minimum voltage coils of switches QTT1 and QTT2 are supplied by a 600/110V mono-phase transformer (T11 and T21, respectively), connected to the switch entry bars. The minimum voltage coil of longitudinal couple G1 is supplied by two 460/110V mono-phase transformers (T41 and T42, respectively), placed in the lighting cabinet and connected to the two general bus systems Bus "A" and Bus "B". The minimum voltage coil of switch J1 is supplied from the auxiliary generator input by means of the T31 460V/110V mono-phase transformer; coil supply (and thus the potential of switch shutdown) is signaled by the yellow lamp on the drawer.

Voltage on the two general bar systems Bus "A" and Bus "B" could be measured with the help of voltmeters PU1 and PU2 as well as of voltmetric selectors SU1 and SU2.

NOTE:

The switching in/release command for switches QTA1, QTA2 is issued by acting the ON / OFF buttons on the control units of same switch. For the command to be carried out the switch must not be blocked due to failure release, and the minimum voltage coil of same must be supplied (the interlocking scheme allows its switching in).

The switching in/release command for switches F1, H1, G1, and J1 is issued by acting upon the ON / OFF buttons on the F1 and H1 switches control unit, i.e. by turning the switch lever in position ON / OFF in the case of switch J1. This switches in if its minimum voltage relay is supplied (the interlocking scheme allows its switching in).

III. VOLTAGE DISTRIBUTION ON 3x460VAC FOR SUPPLYING STATION AUXILIARY SERVICES

3x460VAC voltage distribution, developed by equipment in cabinets D1J... D6J, allows all consumers within and outside SCRN to be supplied with 3 x 460VDC three-phase voltage as well as with 110VDC mono-phase voltage. Voltage is taken from the two general bar systems Bus "A" and Bus "B" and distributed to consumers by means of starters and feeders placed in cabinets D3J, D4J, D5J, and DD6J.

Starters and feeders could be actuated manually or automatically and are developed as plug-in drawers. Their design allows three possible positions, i.e.:

1. plugged in, when the starter can be actuated;

2. plugged out, when the starter cannot be actuated;

3. test position, when only the command part of the starter can be actuated, the power part being disconnected; this position allows startups/shutdowns to be made without supplying the consumer.

The three positions are signaled by an indicator placed on the front side of the drawer. Starters are equipped with two signaling lamps:

- lamp "UNLOCKED", colored in yellow, indicates that the control part is voltage supplied and that the starter can be actuated;

- lamp "START", colored in green, allowing the starter to be started and the consumer to be supplied;

Moreover, starters for star/triangle startup of high-power asynchronous engines are fitted with a red-colored "OVERLOAD" lamp, indicating consumer disconnection by actuating the overload protection.

All starters, except for manual ones, are fitted with a control key placed outside SCRN, usually with the consumer (LOCKOUT). These keys are intended to allow remote startup of starters and lock out their startup whenever the consumer develops maintenance or repair works. The structure of 3x460VAC voltage distribution cabinets is given in the table below.

CABINET NO. 3 DISTRIBUTION D3J

  TABLE D3J

CABINET N0. 4 DISTRIBUTION D4J

  TABLE D4J

CABINET NO. 5 DISTRIBUTION D5J

TABLE D5J

CABINET NO. 6 DISTRIBUTION D6J

TABLE D6J

IV. LIGHTING DISTRIBUTION

Supplying the normal and the safety lighting of the drilling plant as well as inside the station is provided by the lighting cabinet DI. This cabinet provides 460VAC, 110VAC si 24VDC voltage supply of various consumers inside and outside the station, namely:

460VAC : - normal lighting of drilling plant and station;

- controls of cabinets with AC/DC converters;

- controls of power switches;

- 450 kVA transformers' fans;

- condensation proof resistances of the three generators;

- station plugs;

2. 110VAC: - AC/DC converter fans;

- electronic sources of AC/DC converter fans;

- charging rectifiers;

3. 24Vdc: - safety lighting of drilling plant and station;

The 110 VAC three-phase voltage is obtained from the secondaries of the two 450 kVA transformers; each of those supplies a 110 V, by means of a switch (Q1I and Q2I, respectively), between which a transfer couple is inserted. The three switches are electrically interlocked, for the secondaries of the two transformers not to be connected in parallel. This voltage is measured with the aid of voltmeters PU1si PU2, and the voltmetric switches SU1 and SU2, respectively.

The safety 24VDC lighting is ensured by two 12V/200Ah storage batteries serially connected, charged from a rectifier.

The 24VDC consumers are supplied from storage batteries by means of   closed contacts of contactors K1, K2, K3. During normal functioning contactors are closed, being supplied with 110VAC;

Upon cease of alternating voltage contactors open, closed contacts open, thus connecting consumers to the storage batteries.

Safety lighting is provided for both external consumers and for the drilling plant - lighting the hallway, transformers and cabinets compartments.