9/19/12 Substation Main Functions and Classification | EEP

1/6electrical-engineering-portal.com/substation-main-functions-and-classification

electrical-engineering-portal.com

Pr im a r y distr ibu t ion - A lstom 1 4 5 kV Ga s-in su la ted sw itch g ea r - GIS (F3 5 ) a t th e Sh u qa iq HV su bsta t ion in

Sa u di A r a bia

h ttp://electr ica l-en g in eer in g -por ta l.com /su bsta t ion -m a in -fu n ct ion s-

a n d-cla ssifica t ion

Substation Main Functions and Classification

An

electrical substation is an assemblage of electrical components including busbars, switchgear, power

transformers, auxiliaries etc. These components are connected in a definite sequence such that a ckt. can be

switched off during normal operation by manual command and also automatically during abnormal

conditions such as short-ckt.

Basically an electrical substation consists of number of incoming ckt. and outgoing ckt. connected to a

common Bus-bar sy stems. A substation receives electrical power from generating station v ia incoming

transmission lines and delivers elect. power v ia the outgoing transmission lines.

“Substation is integral part of a power sy stem and form important links between the generating station,

transmission sy stems, distribution sy stems and the load points.”

Main tasks of major sub-stations in the T&D

Main tasks associated with major sub-stations in the transmission and ditribution sy stem include following:

1 . Protection of transmission sy stem.

9/19/12 Substation Main Functions and Classification | EEP

2/6electrical-engineering-portal.com/substation-main-functions-and-classification

2. Controlling the Exchange of Energy .

3. Ensure steady State & Transient stability .

4. Load shedding and prevention of loss of sy nchronism. Maintaining the sy stem frequency within

targeted limits.

5. Voltage Control; reducing the reactive power flow by compensation of reactive power, tap-changing.

6. Securing the supply by prov ing adequate line capacity .

7 . Data transmission v ia power line carrier for the purpose of network monitoring; control and

protection.

8. Fault analy sis and pin-pointing the cause and subsequent improvement in that area of field.

9. Determining the energy transfer through transmission lines.

10. Reliable supply by feeding the network at various points.

11 . Establishment of economic load distribution and several associated functions.

Types of substation

The substations can be classified in several ways including the following:

1 Classification based on voltage levels

e.g. : A.C. Substation : EHV, HV, MV, LV; HVDC Substation.

2 Classification based on Outdoor or Indoor

Outdoor substation is under open skv . Indoor substation is inside a building.

3 Classification based on configuration

Conventional Air insulated outdoor substation or

SF6 Gas Insulated Substation (GIS)

Composite substations hav ing combination of the above two

4 Classification based on application

Step Up Substation – Associated with generating station as the generating voltage is low.

Primary Grid Substation – Created at suitable load centre along primary transmission lines.

Secondary Substation – Along secondary transmission line.

Distribution Substation – Created where the transmission line voltage is step down to supply

voltage.

Bulk supply and industrial substation – Similar to distribution sub-station but created separately for

each consumer.

9/19/12 Substation Main Functions and Classification | EEP

3/6electrical-engineering-portal.com/substation-main-functions-and-classification

Mining Substation – Needs special design consideration because of extra precaution for safety

needed in the operation of electric supply .

Mobile Substation – Temporary requirement.

Important Notes:

Prim ary Substations receive power from EHV lines at 400KV, 220KV, 132KV and transform the voltage

to 66KV, 33KV or 22KV (22KV is uncommon) to suit the local requirements in respect of both load and

distance of ultimate consumers. These are also referred to ‘EHV’ Substations.

Secondary Substations receive power at 66/33KV which is stepped down usually to 11KV.

Distribution Substations receive power at 11KV, 6.6 KV and step down to a volt suitable for LV

distribution purposes, normally at 415 volts.

Substation parts and equipment

Each sub-station has the following parts and equipment:

1 Outdoor Switchyard

Incoming Lines

Outgoing Lines

Busbar

Transformers

Bus post insulator & string insulators

Substation Equipment such as circuit-beakers, isolators, earthing switches, surge arresters, CTs,

VTs, neutral grounding equipment.

Station Earthing sy stem comprising ground mat, risers, auxiliary mat, earthing strips, earthing

spikes & earth electrodes.

Overhead earthwire shielding against lightening strokes.

Galvanised steel structures for towers, gantries, equipment supports.

PLCC equipment including line trap, tuning unit, coupling capacitor, etc.

Power cables

Control cables for protection and control

Roads, Railway track, cable trenches

Station illumination sy stem

2 Main Office Building

Administrative building

9/19/12 Substation Main Functions and Classification | EEP

4/6electrical-engineering-portal.com/substation-main-functions-and-classification

Conference room etc.

3 Switchgear and Control Panel Building

Low voltage a.c. Switchgear

Control Panels, Protection Panels

4 Battery Room and D.C. Distribution System

D.C. Battery sy stem and charging equipment

D.C. distribution sy stem

5 Mechanical, Electrical and Other Auxiliaries

Fire fighting sy stem

Diesel Generator (D.G.) Set

Oil purification sy stem

Secondary Distribution

Distribution Substation

9/19/12 Substation Main Functions and Classification | EEP

5/6electrical-engineering-portal.com/substation-main-functions-and-classification

Secon da r y su bsta t ion - V ila lon g a V LG 6 6 /2 0 kV

9/19/12 Substation Main Functions and Classification | EEP

6/6electrical-engineering-portal.com/substation-main-functions-and-classification

Distr ibu t ion su bsta t ion - 2 0/04 kV MCset m eta l-cla d sw itch g ea r (Sch n eider Electr ic)