MERALCO Electrical Design Standards Quiz

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Questions and Answers

What is the required height for accessing a transformer on the 2nd floor when hoisting?

2m measured from the top of the transformer

3m measured from the floor to the bottom of the I-beam

3m measured from the bottom of the concrete

4m measured from the bottom of the I-beam to the floor (correct)

For a two-bank padmount transformer vault located on the ground floor, what are the minimum dimensions?

8m X 4m

8m X 6m (correct)

5m X 4m

6m X 6m

Which of the following is NOT a requirement for the customer vault layout?

Minimum headroom must be maintained according to the specifications

Access door must be encased in concrete

Transformer dimensions must be clearly marked (correct)

Access door must be directly accessible from outside the building

What is the minimum depth required for a one-bank deadfront distribution transformer vault on the ground floor?

5m Signup and view all the answers

What is the minimum depth requirement for a two-bank transformer vault located on the 1st basement floor?

3m Signup and view all the answers

What is the preferred minimum road width for vault accessibility?

6.5 meters Signup and view all the answers

Which of the following is NOT a requirement for standard vault specifications?

Openings to the building interior Signup and view all the answers

What type of transformers are available for vault installation with a secondary voltage of 240Y/139 V?

Three-phase, 34.5 GrdY/20 kV transformers Signup and view all the answers

What is the minimum size requirement for ducts in accordance with PNS 14?

110 mm in diameter Signup and view all the answers

Which of the following is an incorrect specification regarding the transformer vault location?

Vaults may be located in an inner section of the building. Signup and view all the answers

What safety measure is mandated for transformers regarding liquid confinement?

A door sill of 150 mm Signup and view all the answers

What is the primary function of a loop sectionalizing switch in transformers?

To allow for maintenance and safety isolation Signup and view all the answers

Which of the following characteristics pertains to deadfront primary transformers?

Protection features like fuses Signup and view all the answers

What is the recommended cooling capacity for the recommended exhaust fan in a transformer vault?

2500 CFM Signup and view all the answers

Which of the following statements is true about primary and secondary cables in service voltages?

Primary cables operate at voltages up to 34.5 kV. Signup and view all the answers

What is a common requirement for overhead lines according to the standards?

Require surge arresters Signup and view all the answers

What must be included in cable termination for both overhead and underground systems?

Permanent connections Signup and view all the answers

What is the maximum kVA capacity for three-phase transformers with a 240Y/139-V secondary?

1000 kVA Signup and view all the answers

Which feature distinguishes Meralco-supplied Deadfront Distribution Transformers?

Round tank construction Signup and view all the answers

Study Notes

MERALCO Standards: Electrical Design

Standards for electrical design are outlined in MERALCO's Power Up Forum Series.
Electrical Design Team, led by Engr. Eduard Mercado, develops these standards.

Service Voltages

Secondary metering: 240V, 400V, 460V
Primary metering: 34.5kV, 13.8kV (in Cavite & Bulacan), 115kV (subtransmission)

Facilities

Overhead: Pole-mounted transformers, padmount transformers, vault-type distribution transformers (DT)
Underground: Padmount transformers, vault-type DT

Single Line Diagrams

Diagrams illustrate electrical connections for overhead and underground lines feeding a transformer vault.
Key components shown: surge arresters, fuse cutouts/power fuses, cable terminations, primary underground cables, padmounted transformers, secondary cables, current transformers (CTs), and metering devices (often including an elbow arrester and transformer vault).
Civil works, such as concrete-encased PVC ducts, are to be provided by the applicant/customer.

Transformers for Vault Installation

Meralco-Supplied Padmounted Transformers: Three-phase, 34.5GrdY/20kV, or 13.2GrdY/7.62kV. Secondary voltages available are 240Y/139-V (75-1000kVA), 480Y/277-V (500-2000kVA), and 416Y/240-V (500-1000kVA).
Meralco-Supplied Deadfront Distribution Transformers: Single-phase, 34.5GrdY/20kV, or 13.2GrdY/7.62kV. Available in 167–333kVA.
Deadfront primary: Features prominent front for access.
Round tank construction: Design of the tank housing the transformer.
Less flammable liquid filled: Liquid used in the transformer to cool it, is less flammable.
Completely self-protected with fuses: Transformers have internal protection systems integrated with fuses.
Provided with loop sectionalizing switch: Additional safety feature for isolating sections of the circuit.

Standard Vault Location

Preferred: Ground floor; second floor (for DT/padmount XF with hoisting facilities), First basement (for buildings with multiple basements).
Perimeter Location: Vault should be on the building perimeter, near streets/roadways, to access by Meralco trucks/cranes.
Minimum Road Width: 6.5 meters

Standard Vault Specifications/Requirements

Walls and roof: Reinforced concrete, minimum thickness 150mm
No openings: Vault should have no openings to the building interior.
Doorsil: 150mm doorsil required for liquid confinement.
Ventilation: Adequate and permanent ventilation (exhaust fan) with rated capacity of 3/4 HP with 71 cubic meters per minute (2500 CFM).
Clear headroom: 4 meters (minimum) between the bottom of the I-beam and the top of the vault, with 30° sling angle (for hoisting facilities).
Ducts: Primary/secondary ducts, diameter 110mm, thick-walled, red-orange, unplasticized polyvinyl chloride (UPVC), adhering to PNS 14, concrete-encased.
Personnel access pathway: Direct access from outside the building.

Customer Vault Layouts

Specifications for 1-bank and 2-bank padmount transformers in vaults for ground, 2nd floor and 1st basement locations, with minimum dimensions.
Vertical clearances are critical for installing/removing transformers.

Primary Metering

Pole metering structure, follow standards drawing CODE: P-MN03U
Materials, equipment, and labor to be provided by customer.
Components involved.
Diagrams for both overhead (OH) and underground (UG) primary metering layouts.

3 Way RMU with Metering Module

Diagrams showing different vault layouts

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Description

Explore the standards outlined by MERALCO for electrical design in this quiz. Delve into service voltages, facilities, and single line diagrams as established by Engr. Eduard Mercado. Test your knowledge on critical components and their specifications in electrical infrastructure.