Substation Construction, Acceptance Testing and Energization Procedure

Site survey and assessment of the existing connection

The site survey starts by identifying the connection point, voltage level and the distributor’s requirements; this is the basis to define the connection scope and the documents to collect. ^[7][8]

On site, collect a survey report with coordinates and photos, perform a preliminary earthing resistance measurement, record the locations of earthing rods and measured values in the report. When surveying at a plant, review as‑built records, busbar diagrams, transformer documentation and maintenance history to cross‑check field conditions against documentation.

Minimum practical checks include:

• Identify the connection point ID and network type (transmission/distribution) according to the distributor; check available capacity and connection conditions.
• Measure the preliminary total station earthing resistance, record earthing rod coordinates and analyze loop resistance; keep a measurement report with photos for acceptance evidence.
• Inspect cable routes (underground/overhead): cable type, conductor cross-section, sheath condition, burial depth and mechanical protection; note damaged or encroached sections.
• Check transformer location and foundation: safe clearances, platform elevation, drainage and the condition of any fire pit or containment.
• Inspect switching and auxiliary equipment and lightning protection: condition of circuit breakers, isolators, relays, lightning arresters and longitudinal bonding.

Documentation and field evidence required: collect the survey report with coordinates and photos, earthing measurement report, monitoring log, equipment list and test certificates. During the survey, tag/mark field locations for easier cross‑reference during design and acceptance.

Two critical points before construction: if preliminary earthing measurements do not meet requirements, prepare a detailed measurement plan and earthing design; if the cable route or safety corridor is encroached, resolve corridor issues before construction. These risks (missing documents, non‑compliant earthing, infrastructure conflicts) will delay the schedule and require additional documentation.

Summary: complete the survey package as required (coordinates, photos, earthing test report, equipment list) and confirm the connection point ID with the distributor before proceeding to the design and installation planning stage.

Design strategy, approvals and documentation preparation

To obtain connection approval and acceptance for the substation, submit a complete design package including site plan drawings, connection diagrams, schematic diagrams, foundation drawings and equipment technical specifications; include pre‑acceptance test reports. ^[0][0]

Technically, transformer selection must present rated capacity calculations, load factor, no‑load and short‑circuit losses, plus contingency capacity and voltage regulation. When surveying at a plant, provide existing load data, connection configuration and short‑circuit parameters to ensure the selected transformer is appropriate.

Typical minimum documents required:

• Site layout drawings, detailed connection diagrams and main circuit schematics.
• Foundation drawings, clearances and equipment arrangement; earthing layout and lightning protection plan.
• Technical data for transformer and distribution equipment (catalogue, loss data, short-circuit impedance).
• Test reports and pre‑acceptance checks: insulation resistance, dielectric withstand tests, impedance measurements, earthing resistance report.
• Connection agreement / MOA issued by the utility and a description of the connection point.
• Building permits, planning confirmations and location approvals (if applicable).
• As‑built acceptance package, record drawings and equipment logbook for handover to the owner and the utility.

Regarding regulatory compliance and capability, the design/installation entity must meet conditions in relevant regulations (e.g. Circular 21/2020/TT-BCT and related decisions) and hold required competency certificates. During maintenance or at the acceptance/commissioning stage, check signatures, stamps and the utility’s connection agreement before energization.

Common documentation risks include missing detailed connection diagrams, incomplete transformer data or absence of a connection agreement from the utility; such omissions usually delay approval and energization. After approval, prepare record drawings, equipment logbook and test certificates for handover; also perform supplementary field surveys for any missing parameters before formal acceptance.

Equipment supply preparation and material quality control

Verify factory certificates and confirm equipment configuration (transformer, RMU, panels, cables) before shipment to avoid configuration errors that delay acceptance. ^[0][0]

On site, completing document verification is a precondition for provisional acceptance and proposing an energization schedule; when surveying at a plant, missing certificates will interrupt the process.

Documents and technical evidence to check upon equipment receipt:

• Factory release certificate / Certificate of Conformity (COfC), technical catalogue, nameplate data.
• FAT (Factory Acceptance Test) report and incoming inspection report with factory test results.
• Electrical safety test results: insulation resistance, power frequency dielectric tests, transformer ratio/nominal voltage verification.
• Installation drawings, wiring diagrams, auxiliary materials list (bolts, washers, flanges) and maintenance manuals.

During configuration verification, confirm exact model, serial number, wiring style, rated capacity, voltage, transformation ratio, vector group and insulation medium (if applicable).

At the plant, compare the nameplate with the catalogue and PO/contract as a quick step to detect wrong equipment codes; the configuration checklist must link directly to the construction drawings and state acceptable deviations.

If a configuration error or missing certificate is found, the practical handling procedure includes: photograph the issue, quarantine the equipment, issue a non‑conformance (NC) report and coordinate with the manufacturer/supplier for corrective or replacement measures.

Operational warning: do not install or energize without valid insulation resistance and dielectric test results; any unresolved NC will delay acceptance and may require approval from EVN/the utility.

The next stage is typically organizing FAT/SAT, reconciling complete documentation for the acceptance report and confirming legal documents before scheduling energization.

MV–LV installation and on-site safety

Installing MV panels/RMU, pulling and terminating MV cables, assembling the MSB and completing the earthing system must follow a sequence of mechanical checks, electrical tests and safety lockout procedures prior to acceptance and energization. ^[0][0]

On site, an as‑built installation report, complete wiring diagrams and an earthing inspection report are mandatory before any MV compartment is energized. At a plant, check installation location, nameplates, torque of connections, panel straightness, insulation clearances and mechanical earthing connections.

Main installation / inspection steps (summary) include:

• Preparations before works: confirm energization/connection permits, reschedule with the utility (EVN) if needed, maintain a work log, use PPE, secure the area and appoint an electrical safety supervisor.
• Mechanical installation of panels/RMU/MSB: check position, secure bolts, torque according to manufacturer requirements, verify operational gaps and mechanical interlocks; during works inspect mechanical‑to‑earth continuity.
• Pulling and terminating MV cables: confirm cable type, phase marking, strip sheaths per drawings, perform terminations using the correct connector type, torque cable connectors and apply protection; inspect mechanical integrity and measure circuit continuity.
• Earthing system: install earthing conductors, weld/torque joints, check continuity and measure earthing resistance before acceptance.
• Pre‑energization tests: measure phase insulation resistance, check secondary circuits, perform no‑load operational tests of compartments, verify safety interlocks and record test reports.

On-site acceptance checklist (short sample):

Operational warnings: all work on the network must be locked out and clearly signed; if defects are found (loose joints, failed earthing readings, missing documents) stop works, issue a report and rectify before continuing. An electrical safety supervisor and appropriate PPE must be present during works.

If inspection reports, measurement results or equipment documentation are incomplete, suspend acceptance, complete the paperwork and retest; only after compliance should the official energization schedule be coordinated with EVN/the utility.

Testing, technical acceptance and acceptance records

Mandatory tests for substation acceptance include measurements on the transformer, MV panels/RMU, cables/cable terminations, MSB and the earthing system to conclude pass/fail. ^[3][0]

The usual testing sequence starts with document and material verification, followed by passive measurements (e.g. resistance, insulation), then functional tests and protection tests, and finally an overall acceptance prior to energization. On site, check calibration stickers of test equipment and the work log before each test group.

At a plant, tests should be organized in the following order to avoid repeated activities and reduce operational risk:

1. Document check, calibration stickers of measuring instruments and material condition.
2. Passive measurements: winding resistance, earthing resistance, DC/AC insulation resistance tests.
3. Functional/load tests: operation of switching devices, transformer ratio and loss measurements, heat dissipation checks and oil inspections.
4. Protection and relay coordination tests: relay testing, logic checks and time grading verification.
5. Overall acceptance with witness/supervision by the distributor if required.

The table below summarizes test items by equipment and practical inspection criteria on site:

Mandatory acceptance records include detailed signed test reports with pass/fail conclusions, a consolidated technical acceptance report, the work log and any correction records. During maintenance or if failures are detected, prepare remediation reports, specify corrective plans and perform re‑acceptance before commissioning.

For coordination with the distributor/utility, agree on a test schedule and notify safety conditions prior to energization; if witness is required, arrange utility representatives and use signed minutes as confirmation. Operational warning: missing calibration certificates of test equipment or unsigned reports will render acceptance documentation inadequate for energization.

Next, compile the overall acceptance package, attach raw data and signed minutes, then coordinate the energization schedule with the distributor to perform the energization acceptance according to regulations.

Coordinated energization with the utility, handover and operation

Energizing a substation requires complete documentation, confirmation of the connection point with the utility and an approved coordinated switching scenario. ^[0][0]

On site, minimum documentation includes the technical acceptance record, test results, connection diagram, earthing documentation and the electrical safety plan. At a plant, verify consistency between the connection diagram, control panels and field circuit labeling.

Steps to prepare a coordinated energization scenario include: pre‑G hour preparations, pre‑G checks, execute shutdown and energize, monitor/measure after energization and complete the minutes. During maintenance or switching operations there must be an emergency stop point, authorized switching permits and clear assignment of responsibilities for each role.

1. Prepare documents and checklist: design, acceptance records, test results, earthing documentation, permits/insurance if required.
2. Confirm the connection point and schedule with the utility; define time windows and operating conditions before/after energization.
3. Carry out mandatory pre‑energization checks: insulation tests, winding ratio, earthing verification, protection relay and breaker checks, measure leakage current and short‑circuit impedance.
4. Execute energization according to the approved scenario, monitor signals and parameters, handle incidents and record the energization minutes.

Emergency contact list and responsibilities must be printed and available on site; include utility, owner, main contractor, testing agency and safety team. In practice, missing a utility outage window or failing test records commonly cause energization delays.

• Pre‑energization checks: compare test results with documentation, independently verify earthing and validate protection relays.
• Risk mitigation: pre‑acceptance documentation checklist, early factory or pre‑site testing, simulate energization scenarios and perform a PSSR when needed.

The technical acceptance minutes and energization report must state minimum content and signatories with responsibilities. After energization, monitor stability for at least 24–72 hours to confirm no abnormal behavior before final handover.

At the end of energization, the operational handover package should include the handover record, equipment logbook, operation manuals, initial maintenance instructions and a spare parts list. For archiving, digitizing SCADA/DMS documents and operation logs improves traceability during future acceptance checks.