Glossary
Standards, test methods and terms, defined.
The vocabulary used across this site and on site. Definitions describe the published standard or the industry term; where a term maps to a scope we deliver, the service page is linked.
Connections and networks
- Independent Connection Provider
- A company accredited under the National Electricity Registration Scheme to carry out contestable connection works on a distribution network. An ICP designs and builds the connection; the DNO retains the non-contestable works and adopts the completed assets. ICP and Grid Connections →
- Distribution Network Operator
- The licensed operator of the regional electricity distribution network. The DNO issues the connection offer, defines the technical specification for the connection, witnesses key tests and adopts the connection assets on completion. ICP and Grid Connections →
- Contestable works
- The parts of a new connection that a customer may have built by an accredited ICP rather than the DNO. These typically include the HV cable route from the point of connection, the point of connection substation, metering, protection and earthing, and all works on the customer side of the ownership boundary. ICP and Grid Connections →
- Non-contestable works
- The parts of a new connection that only the DNO may carry out: the connection to the existing network, any network reinforcement required to accommodate the new load or generation, and the final adoption inspection. ICP and Grid Connections →
- Point of connection
- The physical point at which a customer installation connects to the distribution network, and the ownership boundary between DNO assets and customer assets. On a generation project the point of connection substation is usually on the critical path to energisation. ICP and Grid Connections →
- National Electricity Registration Scheme
- The UK accreditation scheme, assessed by Lloyd’s Register, under which companies and individual operatives are registered to carry out contestable connection works. DNOs check the published NERS register before accepting an ICP onto a connection. ICP and Grid Connections →
- Final Acceptance Certificate
- The document by which the owner or EPC accepts a completed plant, normally issued after provisional acceptance, the defects period and closure of outstanding snags. The commissioning record pack is compiled against the FAC checklist. Testing and Commissioning →
Standards and codes
- ENA EREC G99
- The Energy Networks Association Engineering Recommendation governing the connection of generation to distribution networks in Great Britain. It sets the compliance testing, protection settings and grid code performance requirements a generator or storage site must demonstrate before it may export. Engineering and Grid Studies →
- ENA EREC G81
- The Engineering Recommendation covering standard design, materials and construction practice for new LV and HV connections, used by DNOs to specify how contestable works must be designed and built. ICP and Grid Connections →
- ENA TS 41-24
- The Energy Networks Association technical specification for the design and installation of earthing systems at substations, including step and touch potential assessment and earth electrode arrangement. Engineering and Grid Studies →
- ENA EREC P28
- The Engineering Recommendation governing voltage fluctuation and flicker limits for plant connected to public distribution networks, assessed as part of a connection application. Engineering and Grid Studies →
- BS 7671
- The IET Wiring Regulations, the UK national standard for low-voltage electrical installations. LV distribution on a utility-scale plant is inspected, tested and certified to BS 7671. Testing and Commissioning →
- BS EN 50522
- The European standard for the earthing of power installations exceeding 1 kV AC, applied alongside ENA TS 41-24 in UK substation earthing design and verification. HV Substation and Cable Works →
- IEC 62446-1
- The international standard for the documentation, commissioning tests and inspection of grid-connected photovoltaic systems. It defines Category 1 tests, applied to every string, and Category 2 tests such as IV curve tracing and thermographic survey where specified. Testing and Commissioning →
- IEC 62852
- The standard covering DC connectors for photovoltaic systems, including the safety and interoperability requirements that govern MC4-type connector assembly and cross-mating. Cable Termination and Testing →
- IEC 60352-2
- The standard for solderless crimped connections, defining crimp quality, tooling and the pull-test acceptance criteria used to verify DC cable crimps on a sample plan. Cable Termination and Testing →
- IEC 60502-2
- The standard for extruded-insulation power cables rated 6 kV to 30 kV, covering the 33 kV XLPE cable and accessories used on UK solar and storage collector systems. HV Substation and Cable Works →
- IEC 60840
- The standard for extruded-insulation power cables and accessories rated above 30 kV up to 150 kV, covering 66 kV and 132 kV XLPE cable, joints and sealing ends. HV Substation and Cable Works →
- IEC 61439
- The standard for low-voltage switchgear and controlgear assemblies, covering the design verification and routine testing of LVAC distribution boards and control panels. HV Substation and Cable Works →
- IEC 60287
- The standard method for calculating the continuous current rating of cables, used in cable sizing alongside BS 7671 where installation conditions, grouping and soil thermal resistivity govern. Engineering and Grid Studies →
- ISO/IEC 11801 and EN 50173
- The standards for generic structured cabling, defining the permanent link and channel performance classes against which CAT5e to CAT7 installations are certified. Cable Termination and Testing →
- EN 50174
- The standard covering information technology cabling installation planning, practice and separation from power circuits, applied to control and communications routing on site. Cable Termination and Testing →
- Distribution Code
- The code setting out the technical requirements governing the relationship between DNOs and the users connected to their networks, including planning, operation and connection conditions. ICP and Grid Connections →
Testing methods
- Insulation resistance test
- A DC test measuring the resistance between conductors, and between conductors and earth, to confirm insulation integrity before energisation. Applied across DC strings, LV circuits and HV cable systems. Testing and Commissioning →
- VLF withstand test
- A very low frequency AC withstand test, normally at 0.1 Hz, used to prove the insulation of installed MV and HV cable systems after termination. Test voltages and durations follow IEEE 400.2. Cable Termination and Testing →
- IEEE 400.2
- The IEEE guide for field testing shielded power cable systems using very low frequency, setting the voltage levels, waveforms and durations for VLF withstand testing. Cable Termination and Testing →
- Sheath integrity test
- A DC test applied between the cable metallic screen and earth to prove the outer sheath is undamaged after installation and backfill. Voltage and duration follow IEC 60229 and the manufacturer requirement. Cable Termination and Testing →
- Tan delta measurement
- A dielectric loss measurement that indicates the overall condition and water-tree ageing of cable insulation. Specified by some clients and DNOs in addition to a withstand test. Cable Termination and Testing →
- Partial discharge test
- A measurement that detects localised breakdown within insulation, joints or terminations before it develops into a fault. Used to verify workmanship on HV accessories where specified. Cable Termination and Testing →
- Time domain reflectometry
- A pulse-echo method used to measure cable length and locate joints, open circuits and faults along a cable route, both before termination and during fault location. Cable Termination and Testing →
- Optical time domain reflectometry
- The fibre equivalent of TDR: a backscatter trace that shows splice loss, connector loss and breaks along an optical link. Traces are recorded bidirectionally and delivered as part of the link certification. Cable Termination and Testing →
- IEC 61280-4-1
- The standard for measuring attenuation of installed multimode and single-mode fibre links, defining the insertion loss method used to certify each link. Cable Termination and Testing →
- IEC 61300-3-35
- The standard defining visual acceptance criteria for fibre optic connector end-faces, applied during inspection and cleaning before mating. Cable Termination and Testing →
- Secondary injection
- A protection test in which currents and voltages are injected directly into the relay inputs to verify settings, characteristics and tripping logic without energising the primary plant. Protection, Control and Switchgear →
- Primary injection
- A protection test in which current is injected through the primary conductor, proving current transformer ratio, polarity and the complete secondary wiring path through to the relay. Protection, Control and Switchgear →
- IV curve tracing
- A Category 2 photovoltaic test that plots the current-voltage characteristic of a string and compares it against the expected curve, revealing mismatch, shading, degradation and connection faults. Testing and Commissioning →
- Thermographic survey
- An infrared survey carried out under load to find hot joints, loose terminations, failed connectors and unbalanced circuits in switchgear, transformer stations, combiner boxes and DC connectors. Operations and Maintenance →
- Step and touch potential
- The voltages that can appear across a person’s feet, or between hand and foot, during an earth fault. Measured and assessed against the limits in ENA TS 41-24 and BS EN 50522 to verify an earthing design. Engineering and Grid Studies →
Plant and equipment
- String combiner box
- The enclosure at which multiple photovoltaic strings are paralleled onto a single DC feeder, containing string fuses, a disconnector and, usually, string current monitoring reported over Modbus. Testing and Commissioning →
- Transformer station
- The skid or containerised unit on a solar or storage plant housing the inverter, the LV/MV transformer, MV switchgear and auxiliary supplies, connecting the array to the collector network. Testing and Commissioning →
- Sealing end
- An HV cable termination that transitions the cable to an air-insulated or gas-insulated connection, providing stress control and environmental sealing. Used at 66 kV and 132 kV on outdoor structures and at GIS bays. HV Substation and Cable Works →
- Separable connector
- A plug-in MV cable termination, in elbow or T-body form, that can be disconnected for testing without cutting back the cable. Common at 11 kV and 33 kV on transformer and switchgear bushings. Cable Termination and Testing →
- XLPE cable
- Cross-linked polyethylene insulated power cable, the standard insulation system for modern MV and HV distribution, manufactured to IEC 60502-2 at 33 kV and IEC 60840 at 66 kV and above. HV Substation and Cable Works →
- Current and voltage transformers
- Instrument transformers that scale primary current and voltage to standard secondary values for protection and metering. Ratio, accuracy class and burden must be verified against the protection scheme they serve. Protection, Control and Switchgear →
- Battery energy storage system
- A grid-connected battery installation, either AC-coupled through its own inverters or DC-coupled behind a shared inverter with generation. Connection, protection coordination and G99 compliance testing follow the same framework as generation. Testing and Commissioning →
- MC4 connector
- The prevailing photovoltaic DC connector family used on module leads, string harnesses and combiner box inputs. Cross-mating between manufacturers is a recognised failure mode, so compatibility is verified against module and combiner types. Cable Termination and Testing →
Communications and control
- IEC 61850
- The international standard for substation automation communications. It defines the data model, the SCD configuration description, and the GOOSE and MMS services used for protection signalling and supervisory data. Protection, Control and Switchgear →
- GOOSE
- Generic Object Oriented Substation Event: the fast, publisher-subscriber multicast messaging service in IEC 61850 used for protection interlocking and trip signalling between devices over the substation network. Protection, Control and Switchgear →
- Modbus RTU over RS-485
- The serial protocol and physical layer most widely used for string monitoring, inverter data and field device polling on solar plants. Correct daisy-chain topology, 120 Ω line termination, bias resistors and single-point shield earthing govern whether a loop is reliable. Cable Termination and Testing →
- SCADA
- Supervisory Control and Data Acquisition: the plant-level system that collects data from field devices and presents control and alarming to the operator. Point to point verification proves every signal from field device to HMI against the signal list. Testing and Commissioning →
- Power plant controller
- The controller that regulates a plant’s active and reactive power at the point of connection to meet grid code requirements, including voltage and frequency response modes and ramp rate limits tested under ENA EREC G99. Engineering and Grid Studies →
Every test on our schedule cites its method and acceptance criterion.
Send the specification and we will tell you which of these apply, who witnesses them and what the record looks like.