1.6 Notification, Connection, Modification, and Inspection Duties
Key Takeaways
- Connecting a new low-voltage electrical installation or energizing a load upgrade requires a formal turn-on application submitted by the appointed LEW to SP Services / SP PowerGrid.
- Before submitting a turn-on application, the Licensed Electrician must physically inspect, test, and issue an official Certificate of Compliance (CoC) confirming full SS 638 compliance.
- Minor electrical repairs (e.g. replacing a faulty socket or light fitting like-for-like) do not require turn-on notification, but major modifications or load additions require LEW certification and SLD updates.
- During the physical supply turn-on, the Licensed Electrician must be physically present on-site alongside the SP PowerGrid meter officer to verify phase sequence, polarities, and earthing integrity.
- Single-Line Diagrams (SLDs) must be prepared using standard symbols, signed and stamped by the LEW, and mounted permanently inside the main switchroom or consumer unit enclosure.
1.6 Notification, Connection, Modification, and Inspection Duties
Quick Summary: Turning on a new electricity supply or modifying an existing installation in Singapore follows a strict legal and administrative workflow involving the Consumer, the Licensed Electrical Worker (LEW), SP Services, SP PowerGrid, and the EMA. The Licensed Electrician must perform mandatory SS 638 initial verification tests, certify an official Certificate of Compliance (CoC), update the Single-Line Diagram (SLD), and attend the joint on-site turn-on with SP PowerGrid.
1. The Step-by-Step Electrical Connection & Turn-On Process
Connecting a new low-voltage supply (up to $45\text{ kVA}$) to SP PowerGrid's distribution network requires executing a six-stage regulatory procedure:
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| SUPPLY CONNECTION & TURN-ON WORKFLOW |
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| STEP 1: APPLICATION & LOAD PLANNING |
| - Consumer engages Licensed Electrician for load assessment (<= 45 kVA). |
| - Submits supply application to SP Services (Customer Services). |
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| STEP 2: ELECTRICAL INSTALLATION & WIRING |
| - Electrician executes/supervises wiring per SS 638 standards. |
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| STEP 3: INITIAL VERIFICATION & TESTING (SS 638 PART 6) |
| - Electrician executes mandatory instrument tests (Continuity, IR, Zs). |
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| STEP 4: CERTIFICATION & SLD PREPARATION |
| - LEW signs Certificate of Compliance (CoC) & endorses Single-Line Diagram. |
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| STEP 5: TURN-ON SUBMISSION & METER APPOINTMENT |
| - Submits CoC & test results to SP Services online portal. |
| - Schedules joint site turn-on appointment with SP PowerGrid officer. |
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| STEP 6: JOINT ON-SITE TURN-ON & ENERGIZATION |
| - LEW & SP PowerGrid officer physically present on-site. |
| - SP PowerGrid fits kWh meter; LEW verifies polarity & turns on main CB.|
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2. Certificate of Compliance (CoC), Statement of Turn On & Mandatory Testing Documentation
The Certificate of Compliance (CoC) is a legal document issued by the LEW in the form approved by the Authority, certifying that an electrical installation has been thoroughly inspected, tested, and verified to be safe and fully compliant with SS 638 prior to connection and energization; a copy is lodged with the market support services licensee (SP Services). At the moment of turn-on, the person turning on the switchgear also issues a Statement of Turn On (SOT) in the form approved by the Authority, acknowledged by the responsible LEW(s) and the person who arranged the connection; no switchgear may be turned on until the consumer’s account with the market support services licensee is activated.
Mandatory Instrument Test Parameters Recorded on the CoC
In accordance with SS 638 Part 6 (Verification), the Licensed Electrician must record precise numerical test results on the CoC documentation:
| Test Parameter | Test Method & Instrument | Mandatory Statutory / SS 638 Minimum Requirement |
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| 1. Protective Conductor Continuity | Low-resistance Ohmmeter ($200\text{ mA}$ DC test current) | Continuous low resistance consistent with conductor length and cross-section; main bonding typically $< 0.05\ \Omega$ (wandering-lead method). |
| 2. Insulation Resistance (IR) | Insulation Resistance Tester ($500\text{ V DC}$ test voltage for LV circuits) | Minimum $1.0\text{ M}\Omega$ between Live conductors and Earth, and between Phase conductors. |
| 3. Polarity Verification | Visual and Continuity Check | Single-pole switches, fuses, and MCBs must be connected strictly in Phase conductors only (never in Neutral). |
| 4. Earth Electrode Resistance | Earth Resistance Tester (3-pole fall-of-potential method) | As low as practical; must satisfy $R_A \times I_{\Delta n} \le 50\text{ V}$ for the RCD protecting a TT installation. |
| 5. Earth Fault Loop Impedance ($Z_s$) | Loop Impedance Tester | Measured $Z_s$ at furthest point must be low enough to trigger automatic disconnection within $0.4\text{ s}$ ($230\text{ V}$). |
| 6. RCD Operation & Trip Timing | Calibrated RCD Tester | At $1\times I_{\Delta n}$ ($30\text{ mA}$), trip time must be $< 300\text{ ms}$; at $5\times I_{\Delta n}$ ($150\text{ mA}$), trip time must be $< 40\text{ ms}$. |
3. Rules Governing Electrical Modifications and Additions
Singapore installation regulations draw a strict legal distinction between minor maintenance repairs and major electrical modifications.
ELECTRICAL WORK CLASSIFICATION
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[ MINOR REPAIRS & REPLACEMENTS ] [ MAJOR MODIFICATIONS & ADDITIONS ]
- Replacing broken socket outlets like-for-like - Installing new final circuits (e.g. EV charger)
- Replacing burnt lighting fittings like-for-like - Upgrading main isolator capacity (e.g. 30A to 63A)
- Replacing blown fuses or MCBs of identical rating - Sub-switchboard additions or solar PV tie-in
- NO turn-on re-application required - REQUIRES LEW testing, updated CoC & SLD
Requirements for Major Modifications
When executing a major modification or extension:
- The Licensed Electrician must calculate maximum demand to ensure the existing intake cable and main isolator are not overloaded.
- The newly installed circuits must undergo full initial verification instrument testing.
- The installation's Single-Line Diagram (SLD) must be updated to reflect the new circuit breakers, cable sizes, and load distribution.
- A revised Certificate of Compliance must be endorsed by the LEW and filed in the site logbook.
4. Single-Line Diagram (SLD) Standards and Display Mandate
Under Regulation 17 of the Electricity (Electrical Installations) Regulations, the licensed electrical worker responsible for an installation must ensure that a clearly drawn circuit diagram (Single-Line Diagram) of the installation is displayed near every switchboard, together with a durable “DANGER” notice showing the operating voltage in English, Malay, Chinese, and Tamil (black text on a yellow background). Every installation must therefore maintain an accurate, up-to-date Single-Line Diagram (SLD).
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| TYPICAL SINGLE-LINE DIAGRAM (SLD) SCHEMA |
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| SP POWERGRID INCOMING SUPPLY (400V 3-Phase 4-Wire AC, 50 Hz) |
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[ SP POWERGRID KWH METER ]
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[ MAIN ISOLATOR: 63A 3-Pole ]
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[ MAIN RCCB: 63A 4-Pole, I_delta_n = 30 mA ]
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[ MCB 6A 1-Pole ] [ MCB 16A 1-Pole ] [ MCB 32A 3-Pole ]
CABLE: 1.5mm2 Cu PVC CABLE: 2.5mm2 Cu PVC CABLE: 6.0mm2 Cu PVC
LOAD : Lighting Circuits LOAD : Socket Circuits LOAD : Air-Con Unit
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| DRAWN BY : TAN AH KOW (LEW ELECTRICIAN 7/012345) |
| LOCATION : 123 KALLANG WAY, #01-01, SINGAPORE |
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Mandatory Features and Display Rules
- Standardized Symbols: SLDs must utilize standardized electrical drafting symbols conforming to IEC 60617 / SS 638.
- Essential Information: The SLD must clearly display the Point of Supply, main incoming cable size, main switch/MCCB rating, meter position, main earthing terminal (MET) connection, RCCB ratings ($I_n$ and $I_{\Delta n}$), MCB circuit ratings, conductor sizes, and connected loads.
- Physical Display Requirement: In commercial switchrooms or DB locations, a physical copy of the SLD—signed and stamped by the LEW—must be framed behind glass or laminated and mounted adjacent to the main switchboard.
During insulation resistance testing of a low-voltage electrical installation prior to supply turn-on, what is the minimum acceptable insulation resistance value specified under SS 638 when testing at 500 V DC?
What is the physical presence requirement for a Licensed Electrician during the official SP PowerGrid supply turn-on appointment for a newly wired premises?
Which of the following electrical site activities is classified as a minor repair that does NOT require submitting a new turn-on application or updated CoC?