Características de la actividad constructora

Í NDICE DE TABLAS

Capítulo 1. El Sector de la Construcción

1.1.3 Características de la actividad constructora

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Over voltage

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Under voltage

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Excessive THD

Include an indicating lamp for each bank of capacitors showing whether a particular step is in operation.

Provide a “general fault” alarm as a volt free set of contacts for connection to the security alarm system.

14.4.9 Control Voltage

Provide a 230 Volt single phase 50Hz or 24 Volt DC power supply at the cubicle for control purposes.

Fuse/circuit breaker protect each control circuit.

14.4.10 Equipment Arrangement

Push buttons, control switches, indicating lights, instruments and similar equipment shall be mounted on the access door(s).

Fully segregated chambers shall be provided between the incoming cable section (which includes the termination and main busbars zones) and the capacitor section and the control section to enable in service maintenance checks to be made without exposure to the high fault energy portions of the cubicle.

14.5 Safety

Incorporate the following safety features:

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Interlocks on each power factor correction cubicle such that access cannot be gained to either contactors or fuses without opening the disconnect device.

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Whenever a contactor is opened automatically, discharge its associated capacitor units in accordance with the requirements of IEC 60871-4.

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No access is to be gained to the capacitor units unless the contactor is open and the capacitors are discharged. Provide either a timer or a voltage detector to prevent access until the residual voltage across each capacitor unit and bank has fallen below 50 volts.

14.6 Equipment Operation

The automatic capacitor bank/s shall be equipped with microprocessor controlled reactive VA control relay/s which shall automatically switch the power factor correction capacitors on and off, via suitably rated contactors and fuse gear, so that the remaining reactive power is reduced.

Capacitor bank: 3 position switch, two of the positions marked "MAN" and "OFF" shall be used for manual operation of the contactor, the third position marked "AUTO" with the switch in this position the contactor is controlled by the power factor control module.

Power factor control module for the capacitor banks with the facility to switch in a maximum of 50 kVAr steps.

Control module operation with the selector switch in automatic:

a) Keep the capacitors disconnected whenever the uncorrected reactive power is below the kVAr setting.

b) Switch in the first bank of capacitors when the uncorrected reactive power rises above the kVAr setting.

c) Switch in further banks of capacitors should the reactive power continue to be above the kVAr setting.

d) Switch out one bank when the corrected reactive power continues to fall more than a specified value below the kVAr setting.

e) Switch out further banks when the corrected reactive power continues to fall more than a specified value below the kVAr setting.

f) 50 kVAr steps or banks of capacitors switched in or out as above.

g) Provide "stopper circuits" where required by the Local Supply Authority.

Steps (b) and (c) and subsequent steps: subject to an adjustable time delay from 0 to 120 secs.

The kVAr setting: adjustable with the actual setting clearly indicated.

The power factor controller shall be capable of accepting a ‘generator running’ signal to disconnect the power factor correction equipment during generator operation.

14.7 Quality

Refer to LV Switchboard section and the following:

Functional test the equipment under load conditions to establish:

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The selected power factor is maintained.

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The equipment is free from hunting.

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The displays are correct.

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The capacitor currents are within the manufacturer's limits.

Recordings of the voltage waveform and its harmonic analysis at the point of equipment connection for each capacitor step.

Other tests as may be required by the Supply Authority.

The equipment will be subjected to an infrared scan/thermal imaging inspection on site after installation connecting of cabling and taking load.

Demonstrate the impedance characteristic of the power factor correction equipment is satisfactory in that it:

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Meets the Supply Authority requirements for providing increased impedance for shunt connected capacitors.

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Will not resonate with the power transformer or load at any harmonic frequency.

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Limits harmonic currents in the capacitors to within the manufacturers limits.

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Compliance is required for both the initial and up to and including the ultimate configuration.

14.8 Assemblies

Refer to LV Switchboard section and the following:

14.8.1 Ventilation

Provide ventilation as required for each cubicle in such a way as to ensure the capacitors and associated equipment operate in an ambient temperature less than the recommended maximum ambient temperature for the equipment.

Provide forced ventilation for the cubicles in such a way as to ensure the capacitors and associated equipment operate in ambient temperatures less than the recommended maximum temperatures for the temperature category selected in accordance with IEC 831.

Provide mesh covering to the ventilation openings to prevent vermin entering the cubicle.

Provide thermostatically controlled ventilation fans.

14.9 Proprietary Assemblies