MEDUIM VOLTAGE SWITCHGEAR

MEDUIM VOLTAGE SWITCHGEAR&

INDOOR TRANSFORMER SUBSTATION

 

PART 1 GENERAL

3.4.1.1 RELATED DOCUMENTS

a. Drawings and general provisions of Contract, including
General and special Conditions, General requirements apply to work of this section.

b. General Provisions for Electrical Work, Section 3.1, 3.2 apply to work of this section.

3.4.1.2 DESCRIPTION OF WORK

Work includes providing all materials, equipment, accessories, services and tests necessary to complete and make ready for operation by the Owner, switchgear in accordance with Drawings and Specifications.

3.4.1.3 QUALITY ASSURANCE

A.         Manufacturers: Firms regularly engaged in the manufacture of switchgear of the types and capacities required, whose products have been in satisfactory use in similar service for not less than 5 years.

B.         Standards Compliance: Comply with requirements of applicable local codes and DIN/VDE, and IEC. Standards pertaining to switchgear. Provide service entrance label and applicable service entrance features per local code and NEC· Provide switchgear products and components which' have been UL      listed and labeled·

  3.4.1.4 SUBMITTALS

a - Product data: Submit manufacturer’s data for switchgear including sizes,    enclosures, and electrical ratings and characteristics. 

b - Shop Drawings: Submit dimensional layout on architectural background        drawings of switchgear, single-line diagram, and outline drawings.

C - Relay co-ordination:

Submit ready and circuit breaker co-ordination study.

     The current-time characteristics must be plotted on a log-log papers showing that the choice of the C.B. settings are correct for co-ordination.

 D - Submit to Electricity distribution Co. for approval layout plans, risers and loading schedules with medium voltage switchgear transformers and ring main units.

PART 2    PRODUCTS:

3.4.2.1 INSPECTION

A.         Examine conditions under which switchgears are to be installed Notify Architect in writing of conditions detrimental to proper completion of the work; do not proceed with work until unsatisfactory conditions have been corrected.

B.         Routine works tests shall be carried out at the manufacturers works in the presence of the consultant.

PART 3 INSTALLATION

A.         Install switchgears as indicated accordance with manufacturer's written instruction, requirements of applicable standards, NECA's "Standard of Installation," and in accordance with recognized industry practices to ensure that installation complies with requirements and serves intended function

B.         Coordinate as necessary to interface installation of switchgear with other work.

C.        Mount the switchgear assembly on floor steel aligning channels elevated above floor level by a concrete pad and as noted on drawings. Provide shims to achieve level installation.

D.        Insure that switchgears are shipped in sections which can be fitted through the structures available.

E.         Bond together the switchgear structure, sections and all
conduits terminating at same with a 120 ram 2 bare copper earth cables and connect to the switchgear earth bus and to the earthing loop as required. Provide conduits terminating at switchgear with Earthing Wedges of the required size.

F.         Tighten electrical connectors and terminals including screws and bolts, in accordance with equipment manufacturer's published torque tightening values for equipment connectors. Where manufacturer's torquing requirements are not indicated, tighten connectors and terminals to comply with tightening torques specified in UL Standard 486A and B.

G.        Provide insulation mat in front of switchgear and rear of freestanding equipment and extend 30cm beyond ends.

H.        Provide protective covering during construction.

I.          Touch up marred or scratched surfaces to match original finish.

J.         Provide fuses of the ratings indicated, with one complete set of spare fuses for each rating.

K.         Adjust operating mechanism for free mechanical movement

3.4.3.4 FIELD QUALITY CONTROL

A.         Upon completion of installation of equipment and after circuitry has been energized, test equipment to demonstrate compliance with requirements When possible, field-correct malfunctioning units, then retest to demonstrate compliance; otherwise remove and replace with new equipment and retest.

B.         Prior to energization of switchgears:

1.         Megger check phase-to-phase and phase-to-ground insulating resistance levels of conductors

2.         Check switchboard for continuity and for short circuits.

C.        Set all circuit breaker trip ratings for maximum coordination 

With upstream and downstream devices, including ground fault trips where supplied.

D.        Subsequent to wire and cable hook-ups, energize equipment and demonstrate functioning in accordance with requirements.

E.         Open and close load break switching devices under load.

3.4.3.4 PERSONNEL TRAINING

A.         Building Operating Personnel Training: Train Owner's building personnel in procedures for starting up, testing and operating H.V. switchgear and auxiliary equipment. Furnish three operator's manual providing installation and operating instructions for the H.V· switchgear.

INDOOR TRANSFORMERS SUBSTATION

PART4 - PRODUCTS

3.4.3.1 GENERAL.

A.        Supply, install and commission Transformers sub-station complete including:

-                22 KV ring main unit.

-                Oil  type Transformer(s).

-                All necessary fixing and connection equipment and accessories required for a complete and operable system.

B.   Ensure that the space allocated for the medium voltage switchgear and the transformers is in accordance with the requirements and supplied by the manufacturer. Any inaccuracy in the building once built, shall be corrected as required and directed by the Consulting Engineer and at no extra charge to the Employer.

3.4.3.2 RING MAIN UNITS

A.        GENERAL

a-         Each ring main unit comprises three No., three-pole load break switch switches rated 630 Amps for incoming feeders and one three-pole load break switch 630 A for the cable connected to the M.V. switchgear.

(400A for the cable connected to transformer)

b-         Cable termination boxes shall be provided for the incoming and outgoing, also for the feeder to the 22KV switchboard, having the following characteristics:

c-     Incoming and outgoing feeders, to be as used by the Electric Power   Distribution Company, coordinate with local power authority in this respect.

            The 22 KV switchboard feeder, 3-Core, XLPE insulated armoured with 240 sq.mm. Aluminum conductor.

B.        TECHNICAL DATA:

The ring-main-unit shall fulfill the following data

a.         Type                                                                Load break switch

b.         Rated voltage                                                  22 Kv

          c.         Rated current :

-           Transformer load break switch           400A

-           Ring main load break switches           630 A.

          d.         Short circuit level                                            25KVA

e.         Impulse withstand voltage

            1.2/50 u sec ( KV Peak)                                 75KV.

f.          Rated insulation level, one minute

Withstand voltage, 1 min., 50 Hz.                   35 KV

g.         Fuse rating ( A )                                              As indicated in the Drawings

.

MV switch gear (if needed by the authority)

To be with SF6 C.B. with the same specifications as above while ratings to be as shown on the drawings

3.4.3.4 TRANSFORMERS.

A.         Transformers shall be of the indoor type, low losses,  dry type, two windings, four  off- load taps 2 x 2.5% on the high voltage side, in compliance with the requirements of IEC      recommendation No. 76, parts 1 to 5 inclusive.

B.         Transformer data:

-           Rating                          KVA as indicated in the drawings.

-           Primary voltage          22000 Volts

-         Secondary voltage       380 Volts

-         Vector group                  Dyn 11

-           Off-load tapping          +/2 x 2.5%  (H.V.) of phases No.

-           Frequency                   50 Hz

                                     Ambient temperature   (average)                  45

-            Impedance at principle tapping        6 %     

 -          Terminal arrangements:         H.V. cable box for

XLPE insulated, armoured 3-core Alum. Cable, 3 x 240 mm2 cross section area.

-           L.V suitable connection for cables

-           Transformers shall be cooled by natural air convection.

C.        The transformers shall be equipped with control units and temperature sensors in order to perform alarm, tripping and controlling the ventilation fan installed in the transformer room.

D.        The transformers shall be provided with noise reduction support blocks in order to reduce the noise level.

E.         Following tests shall be carried out according to IEC standards and include:

a.         Turns-ratio test

b.         Insulation tests between windings and between windings and earth.

c.         Induced high voltage test.

d.         No-load losses test.

e.         Short circuit test.

f.          Winding resistance measurement.

g.         Loading and heat test

h.         Resistance of insulation to impulse test.

3.4.3.4 EQUIPMENT DATA/SHOP DRAWINGS

A.         Shop/construction drawings for installations covered under this sub-section shall include but not be limited to the following:

B.         Construction and installation details for the M.V. switchboards cables and transformers.

C.        Front elevation of switchboard, one line diagram showing
current and voltage transformers With ratios, instruments, switches, relays, trip ratings.

D.        Floor plan and top views showing locations of power and
control conduit, ground cable entries and size, location and arrangement of tie bus-way.

E.         Bill of material of switchgear summary listing all major components.

F.         Details of connection of cables to transformers and main distribution boards.

G.        Wiring and schematic diagrams of power, control, relay, metering and similar circuits. The separate schematic diagrams shall include complete three line diagrams of 22 kV ring main units, and all instruments, switches, instrument

Transformers, auxiliary contacts, relays and any other devices in this switchgear

H.        Handling, installation and assembly drawings.

J.         Key interlocking scheme showing key numbers and operations performed Dimensioned outline drawings and sectional switchgear views.

K.         The equipment data to be provided prior to ordering any material covered by this Sub-section shall include but not be limited to the following:-

L.         Complete technical data on circuit -breakers and other switchgear including data operating characteristics, compliance with standards, dimensions and weights, detailed description, operating mechanism etc.

M.        Complete technical data on instrument transformers, protective and auxiliary relays, measuring instruments including manufacturer's catalogues, operating characteristics, operating curves, detailed description etc.

N.        Complete technical data on the construction of the switchgear, with provision for expansion including manufacturer’s catalogues.

3.4.3.5 ACCEPTABLE MANUFACTURERS

A.          EMG                          (EGYPT)

          B.         ABB ARAB                 (EGYPT)

Or approved equal

PART 5 - EXECUTION

3.4.5.1 INSPECTION

A.         Examine conditions under which transformer substations are to be installed. Notify engineer in writing of conditions detrimental to proper completion of the work Do not proceed with work until unsatisfactory conditions have been corrected.

3.4.5.2    INSTALLATION

A.         Install transformer substations as indicated in accordance with manufacturer's written instructions, requirements of applicable standards, and in accordance with Electricity Co and local authority requirements to ensure that installation complies with requirements and serves intended function.

B.         Coordinate as necessary to interface installation of
transformers with related switchboards and other work.

C.        Tighten electrical connectors and terminals, including screws and bolts, in accordance with equipment manufacturer's published torque tightening values for equipment connectors.

D.        Provide protective covering during construction.

E.         Touch-up marred or scratched surfaces to match original finish.

F.         Adjust fans when so furnished for free mechanical movement.

3.4.5.3 FIELD QUALITY CONTROL

A.         Upon completion of installation of equipment, and after
circuitry has been energized, test equipment to demonstrate compliance with requirements. Where possible, correct malfunctioning units, then retest to demonstrate compliance; otherwise, remove and replace with new equipment and retest at no additional cost to Owner.

B.         Prior to energization of transformers and related distribution equipment:

1.         With manufacturer’s approval, perform phase-to-phase and phase-to-earth insulation resistance tests utilizing a megohmmeter with minimum test voltage output of 5,000 volts DC with a minimum resistance of 25,000 megohms. The test duration shall be for 10 minutes with resistance tabulated at 30 seconds, (1) minute and 10 minutes. Dielectric absorption ratio and polarization index will be calculated.

2.         Check transformers for continuity and for short circuits.

                   3.         Notify Architect of any abnormalities.

C.        Subsequent to wire and cable hook-ups, energize transformers and demonstrate functioning in accordance with requirements.

D.        Provide manufacturer's recommended DC high potential test for transformers and verify acceptability of results prior to energizing.

End Of This Section