Construction of 220 kV Lafarge substation. Book 1 “Electrical solutions”, страница 5

   Earthing of the metal blocks, equipment cases, switchgear, and other metallic parts which may turn out energized owing to damage isolation, is implemented by the way of creation of electric contact with substation ground circuit.

Parts of metal blocks for the creation ground loop join together by welding, equipment cases are earthed by flexible communications on a metalware of blocks

5.3. Short circuit currents at buses 220, 35 and 6.6 kV calculation. Selection and test of 35 kV cables.

Expected short-circuit currents at buses Lafarge substation and Quarry substation for the period of entry into operation are shown in the Table 1.                                                                                                

 Table 1

Short circuit point	Current from the system (kA)	Seed current from motor (kA)	Current on the buses (kA)
220kV Lafarge substation buses	8,21   (22,87)	-	8,21  (22,87)
35kV Lafarge substation buses	9,25 (24,59)	-	9,25 (24,59)
6,6 kV Lafarge substation buses	26,31 (69,58)	11,68 (29,73)	37,99 (99,31)
35kV Quarry substation buses	6,25 (11,14)	-	6,25 (11,14)
6,6kV Quarry substation buses	6,46 (15,53)	1,1 (2,8)	7,56 (18,33)

Short circuit currents at buses Lafarge substation and Quarry substation, taking into account further extension to Cement mill 2 and 3, are shown in the Table 2.

   Table 2

Short circuit point	Current from the system (kA)	Seed current from motor (kA)	Current on the buses (kA)
220kV Lafarge substation buses	8,21   (22,87)	-	8,21  (22,87)

35kV Lafarge substation buses	9,25 (24,59)	-	9,25 (24,59)
6,6 kV Lafarge substation buses	26,31 (69,58)	20,32 (51,73)	46,63 (121,31)
35kV Quarry substation buses	6,25 (11,14)	-	6,25 (11,14)
6,6kV Quarry substation buses	6,46 (15,53)	1,1 (2,8)	7,56 (18,33)

5.5. Electricity supply auxiliary  system

5.5.1. Auxiliary scheme (67177-811/821- ИОС1.1_page.4)

The main auxiliary consumers on the planned substation are  electric load, classified by the degree of reliability of electricity supply to consumers category I-III.

The main auxiliary consumers at the Lafarge 220 kV  substation are electric cooling systems of power transformers 63 MVA, motors and heating elements of the ventilation system, electric heating in rooms, lighting, electric motor drives and switch-disconnectors (outdoor switchgear 220 kV , switchgear 35 kV and switchgear 6.6 kV), Relay Protection and Automation, Automated Control System, etc.

For auxiliaries electric load feeding in substation provides areal separated auxiliaries boards.

The distribution of auxiliaries consumers' between boards is performed according to geographic location.

For electrical power supply of receivers installed on substation, is provided installation of two 6,6/0,4кВ auxiliary transformers and capacity each of it is 630kVA (831TF05 and 831TF25).

The auxiliary transformers are connected to different switchgear and control gear sections 6,6 kV, which are feeding from the winds of low voltage 6,6 kV autotransformers 63 МВА. In emergency operation buses power 6,6 kV is implemented from diesel-generator installation (828GN03EC10) through step-up transformer 0,4/6,6 kV with the capacity 1600 kVA (828 TF03).

Auxiliaries scheme is implemented according to design brief.

To ensure power supply especially critical consumers of their own needs at the substation provides backup power from an independent source - batteries.

In normal mode electrical power supply of auxiliaries electric load is implemented from one of the auxiliary transformers, the second is in reserve.