1.4 Metering Enclosures, Labelling & Distribution Point Rules

1.4 Metering Enclosures, Labelling & Distribution Point Rules

Overview of DEWA Revenue Metering Rules

Accurate electricity metering is essential for utility revenue collection and power management across Dubai. Electrical contractors are responsible for providing fully compliant meter cabinets, Current Transformer (CT) chambers, potential test blocks, and protective wiring in strict accordance with DEWA specifications. All revenue meters, CT secondary wiring seals, and test blocks remain the exclusive property of DEWA and may only be installed, calibrated, programmed, and sealed by authorized DEWA personnel.

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Direct Metering vs. Current Transformer (CT) Metering

DEWA categorizes low-voltage revenue metering into two primary technical topologies based on total connected electrical load and per-phase operating current.

1. Direct Metering (Whole-Current Smart Meters)

• Applicability & Threshold: Mandatory for low-voltage consumer installations with a total operating current rating up to 125 A per phase (corresponding to connected loads up to approximately 70–80 kVA).
• Operating Principle: Incoming DEWA phase and neutral conductors connect directly to the main terminal blocks of the DEWA whole-current smart meter. The total load current flows directly through the meter's internal measurement shunts.
• Enclosure & Placement Rules: Direct meter cabinets must be mounted outdoors on villa boundary walls or in dedicated ground-floor meter rooms (for multi-tenant commercial or residential developments). Meters must be positioned at an eye-level height of 1.4 m to 1.6 m from finished floor level to the center of the display, allowing easy access for DEWA personnel.

2. Current Transformer (CT) Metering

• Applicability & Threshold: Mandatory for all electrical installations where per-phase current exceeds 125 A (connected loads exceeding 80 kVA up to main MDB ratings of 2500 A+).
• Operating Principle: Passing high primary currents directly through a meter is unsafe and impractical. Precision Current Transformers (CTs) are installed around main phase busbars within a dedicated, sealable CT Chamber housed inside the Main Distribution Board (MDB). The CT secondary step-down current (standardized 5 A secondary output) feeds the remote DEWA CT smart meter.
• Technical CT Specifications:
  • Secondary Output: 5 A (e.g., standard CT primary/secondary ratios: 200/5A, 400/5A, 800/5A, 1600/5A, 2500/5A).
  • Accuracy Class: Class 0.5S or Class 0.2S per IEC 61869-2 for high-precision revenue metering.
  • Potential Test Block (PTB): A sealable, multi-terminal Potential Test Block must be installed adjacent to the CT meter, enabling DEWA engineers to safely test voltage/current signals without interrupting main power.

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Phase & Conductor Color Coding Standards

To ensure maintenance safety and prevent phase-crossing faults during installation, Dubai strictly enforces wiring color standards.

Harmonized Color Coding (IEC 60446 / BS 7671)

All new low-voltage electrical installations in Dubai must use harmonized conductor insulation colors:

• Phase 1 (L1): Brown
• Phase 2 (L2): Black
• Phase 3 (L3): Grey
• Neutral (N): Blue
• Protective Earth (PE): Green-and-Yellow (dual bi-color striped insulation along entire length).

Legacy Color Coding (Existing Installations)

When performing retrofits or alterations on older existing buildings in Dubai, engineers will encounter legacy color codes:

• Phase 1 (L1): Red
• Phase 2 (L2): Yellow
• Phase 3 (L3): Blue
• Neutral (N): Black
• Protective Earth (PE): Green or bare copper.

Mandatory Dual-Color Warning Notice

Where legacy and harmonized color systems co-exist within the same panelboard or facility alteration, a permanent warning label MUST be affixed to the panel face:

CAUTION: THIS INSTALLATION CONTAINS BOTH HARMONIZED AND LEGACY WIRING COLOR CODES. CONDUCTORS MUST BE POSITIVELY IDENTIFIED BEFORE SERVICING.

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Ingress Protection (IP) & Mechanical Protection Ratings

Due to Dubai's severe summer heat, dust storms, and coastal humidity, electrical enclosures must satisfy rigid Ingress Protection (IP) ratings per IEC 60529:

• Outdoor Meter Cabinets & External DBs: Minimum IP55 (dust-protected and protected against water jets from any direction) or IP65 in exposed locations. Outdoor enclosures must be fabricated from UV-stabilized Glass Reinforced Polyester (GRP) or powder-coated Grade 316L stainless steel.
• Indoor Electrical Rooms: Minimum IP54 or IP42 in air-conditioned plant spaces.
• Bottom Cable Entry Rule: All cable entries into outdoor weatherproof enclosures MUST enter from the bottom panel only via certified brass cable glands with neoprene shrouds. Top or side entries are prohibited to prevent water ingress.

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Labelling, Warning Notices & Distribution Board Rules

Clear, indelible labeling is mandatory across all switchgear, meter cabinets, and distribution boards.

Warning Labels & Specifications

• Material: Permanent rigid trifoliate (engraved laminated plastic) fastened with screws or rivets. Adhesive tape labels are strictly prohibited.
• Mandatory Engraved Warning Notices:
  • Main Intake / Switchboard: "DANGER 400V - DEWA SUPPLY INTAKE"
  • Dual Supply / Generator Interlock: "WARNING: DUAL SUPPLY - ISOLATE BOTH MAINS AND STANDBY GENERATOR BEFORE SERVICING"
  • Revenue Metering: "DEWA REVENUE METER - TAMPERING OR BREAKING SEALS IS A PUNISHABLE OFFENCE"
  • Main Earthing Terminal: "SAFETY ELECTRICAL CONNECTION - DO NOT REMOVE"

Circuit Directory Requirements

Every distribution board must feature a typed, durable circuit directory card inside a protective sleeve on the inner door face detailing circuit numbers, phase allocations (L1, L2, L3), connected load descriptions, MCB ratings, RCD sensitivities (mA), and cable cross-sections (mm²).