Service Protection Device is a safety component in electrical installations, designed to interrupt fault currents between the main switchboard and the network. It ensures the protection of electrical systems and sensitive equipment from voltage surges.
Purpose
- • Protects electrical systems from faults and surges.
- • Allows for the disconnection of specific supplies without affecting the entire property.
- • Required by law to be installed and maintained as a tamper-proof device.
Key Definitions
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Service Fuse
Historically used to refer to a Service Protection Device. This definition is now considered obsolete but retained for clarity in external references. -
Service Protection Device (SPD)
The first line of protection, located on the installation side of the Connection Point, as per Clause 4.7.
Coordination of Protection Devices
All protection devices within an electrical installation must operate in a manner that prevents faults from triggering devices in the distribution system. Coordination or grading of protection devices is mandatory as per the electricity distributor’s requirements.
Accessibility Requirements
Service and load control equipment must be accessible to distributor officers during normal working hours. If metering equipment is not adjacent to the SPD, its location must be clearly labeled on the main switchboard in compliance with Clause 4.17.
Installation Specifications
Free Length of Consumer Mains/Underground Service
- • Above Fuse (Line Side): Minimum 75mm
- • Below Fuse (Load Side): Minimum 150mm
- • Neutral conductor must match these lengths.
- • All connections must be made by an accredited service provider.
Service Protection Device Requirements
- • Installation: Customers must provide and maintain an approved SPD.
- • Fuse Carrier Ratings: The maximum rating for the fuse assembly must be equal to or greater than the fuse element rating, with a minimum of 100 amps.
- • Anti-Intrusion Assembly: Fuse assemblies must have a sealable escutcheon to prevent access to terminals, while the carrier need not be sealed to the base.
Combined Devices
For single customer installations (e.g., 100A single domestic), the functions of an SPD and a Meter Protection Device (MPD) can be combined into one physical device if compliant with Clause 4.7.2.
Location Requirements
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Meter Protection
Must always be on the installation side of the SPD. -
Demand Determination
- • For a maximum demand up to 100A per phase or meter rating, the SPD is located on the distribution network side of the meters.
- • For demand exceeding these values, the SPD must be adjacent to or incorporated into the main switchboard on the line side of current transformers.
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Height Regulations
- • Maximum height: 2.0m from the top of the device.
- • Minimum height: 0.5m from the line side terminals above ground level.
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Alterations to Existing Installations
These requirements apply unless upgrading the service, consumer mains, or switchboard is necessary, in which case the existing SPD location may be retained.
Service & Meter Protection Fuse Requirements
Notes
- 1) These examples are dependent on the loading of the various metered sections of an installation.
- 2) When using service protection devices of the larger sizes you must ensure that grading is achieved below those fuses. The grading prevents nuisance loss of supply as the Meter Protection fuse then protects a smaller portion of the installation by ensuring that the fault is seen by the fuse which is closest to the fault (between the fault and the supply).
- 3) With supplies direct from a substation, grading must be achieved.
- 4) Multiple 100 Amp service protection fuses per phase are allowed, when there is a single service protection device protecting the whole installation – contact your distributor for more information with each case.
- 5) Number of customers per 100 amp service protection device/fuses is determined by the requirements of Clause 4.13.
- 6) For existing installations this rating must be reduced to reflect the current rating of existing consumers or sub mains and to accommodate load limiting in accordance with AS/NZS 3000 requirements.
- 7) This is a maximum rating for an MPD HRC fuse and may be reduced for installations with a lower maximum demand.
- 8) In accordance with Annexure Clause 2.8.2 (at time of publication), an MPD can be a Circuit Breaker but in any case must have time current characteristics that do not exceed that of an 80 amp HRC fuse. A circuit breaker MPD can be used as a load limiting device as per AS/NZS 3000.
Fuses for Combined Service Protection Device and Meter Protection Device
100 amp single domestic premises. The service protection fuses and meter protection fuses must comply with the following requirements:
- a) The service protection fuse assembly must accept a Type 11b 80A or 100A current limiting (HRC) fusible link. The fusible link must be manufactured in accordance with AS60269.3.0 and AS 60269.3.1*.
- b) The equipment must be supplied complete with the fusible link, fuse carrier, base, and sealed escutcheon.
- c) The fuse base may be either front or back connected.
- d) The fuse base must have two load terminals, or you must provide a sealable active link for connection of more than one tariff or customer.
- e) Connect one conductor only to each separate terminal. Protect unused terminals from accidental contact.
- f) Where the service and/or meter protection device consists of a base, insulating cover (turret), and fuse carrier, you must install and secure the insulating cover (turret) before the fuse carrier is inserted.
- g) Where insulating barriers are provided on one terminal only, you must use that side of the fuse base for the line side connection. (Do not remove barriers.)
- h) If you have to use specialized insulated tools to make connections into the fuse base, you must follow the switchboard manufacturers instructions.
- i) The fuse-link dimensions are shown in Figure 4-2.
- j) Bolt-in style motor start fuses are an acceptable alternative to the fuse shown in Figure 4-2. Note: Bolt-in style motor fuses are not standard. Where used, a spare set of fuse links is to be provided by the customer.
Note: Electrical installations on railway land in the 1500V DC electrified track area normally require circuit breakers as service protection devices.
100A Fuse Link Dimensions
Handling and Disposal of HRC Fuse Links
Asbestos Containment
- • HRC fuse links may contain friable asbestos materials.
- • Damage to the fuse links can release asbestos fibers, posing health risks.
- • When replacing fuse links, ensure they are removed and disposed of as asbestos waste. Follow local regulations and guidelines on hazardous waste disposal.
Personal Protective Equipment (PPE)
- Use appropriate PPE, including gloves, masks, and protective clothing, when handling fuse links.
Enclosures for Service Protection Devices Exceeding 100A
Design and Installation
- Enclosures must adhere to Appendix ZC of AS 3439.1, focusing on arc fault minimization.
Specifications for Service Protection Devices
- Service protection devices rated above 100A must comply with:
- • AS 60269.21
- • IEC 269 Part 2-1: Low Voltage Fuses
- • BS 88 Part 2, 1975: Low Voltage Fuses
- • AS 60529-2004: Degrees of protection provided by enclosures (IP Code)
Requirements
- • Must accommodate current limiting (HRC) fuses rated between 200A to 400A.
- • Must utilize HRC fuse links that comply with Class Q1, BS 88 Part 2, 1975.
- • Minimum rated voltage of 500V and breaking capacity of at least 80kA.
- • Provision for solid links as requested by the distributor.
- • Fuse-link dimensions must conform to specified standards (B4 or C1 for bolted connections; Size 2 for blade connections).
- • Incorporate phase segregation to prevent phase-to-phase faults.
Safety Features
- • Insulated enclosures with sealed covers.
- • Ensure no live parts are exposed during sealing.
- • Fuse assemblies can be front or back connected.
Controlled Load – Contactor Wiring
This image illustrates a diagram for electrical installation requirements. It features a contactor and associated wiring for systems where the controlled load exceeds 25A or involves multi-phase switching. The contactor is positioned at the meter, with a dedicated switch to control the contactor coil. Both the circuit breaker and contactor covers are designed to be sealable for safety. The diagram primarily shows a single-phase setup for clarity, while also noting that an alternate location for the main switch could be on the load side of the contactor.
Circuit Breakers in Lieu of Service Protection Fuses
Circuit Breaker Specifications
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Circuit breakers may be used instead of 100A service protection fuses under the following conditions:
- • Fault current limiting type.
- • Rated short circuit current capacity must meet or exceed prospective short circuit current.
- • Coordinate with electricity distributor’s protection settings.
- • Must have a locking mechanism in the ‘off’ position, comply with AS 3947.2, and allow sealing of adjustable settings.
Installation Guidelines
- • Ensure all connections are enclosed and sealed to prevent unauthorized access.
- • Maintain the circuit breaker according to manufacturer specifications.
Connection and Identification of Service Protection Devices
Connection Guidelines
- For vertically mounted devices, connections should be at the top. If not feasible, ensure proper labeling of the line side.
Identification Requirements
- • Clearly mark each fuse with its rating.
- • If the devices are not easily visible, include a notation on the metering panel with their location.
- Ensure all labeling is durable and legible, following AS/NZS 3000 standards.
Rewireable Fuses
Replacement Guidelines
- When modifying services or conducting work on existing rewireable fuses, replace them with compliant service protection devices per Clause 4.7.
Maximum Conductor Sizes
Conductor Specifications
- The maximum conductor cross-sectional area terminated at a 100A service protection device must not exceed the terminal design specifications.
Maintenance and Sealing Procedures
Maintenance Responsibilities
- Seals on service protection devices that are broken must be re-sealed by authorized personnel (metering provider, Level 2 authorized person, or electricity distributor). Be aware that a charge may apply for this service.