Substation Construction

Substation construction refers to the full range of engineering activities—civil works, electrical equipment installation, commissioning, and energization—required to build a facility that transforms voltage, distributes power, controls power flow, and protects the power system. It is a core component of power grid infrastructure, covering the entire lifecycle from site selection, design, and civil construction (e.g., gantry foundations, equipment foundations, control buildings) to the installation of primary equipment (transformers, circuit breakers, disconnectors, busbars) and secondary systems (protection, monitoring, communication), followed by system testing, commissioning, and grid connection. The quality of substation construction directly affects the safety and stability of the grid, reliability of power supply, and the integration of renewable energy. In overseas projects, additional challenges include compliance with local standards (e.g., IEC, IEEE), environmental conditions (high temperature, humidity, seismic, pollution), logistics, and local management. Substations are typically categorized as step-up, step-down, switching, or converter stations, and construction must strictly follow design drawings, technical specifications, and safety regulations while coordinating multiple disciplines.

In-Depth Interpretation of Substation Construction: Standard Systems and Practical Key Points from the Perspective of Overseas General Contractors

I. Definition and Background

Substation is a core facility in the power system for voltage transformation, centralized distribution, control and protection, and power dispatch. By function, it can be classified into step-up substations, step-down substations, switching stations, and traction substations; by insulation medium, it can be classified into air-insulated (AIS), gas-insulated (GIS), and hybrid (HGIS); by layout, it can be classified into outdoor, indoor, and underground types. In the context of overseas engineering, substation construction typically covers the full chain of work including civil works, primary equipment installation, secondary system integration, communication and SCADA interfacing, grid connection commissioning, and O&M training.

From a background perspective, the standard system for substation construction is highly fragmented. IEC (International Electrotechnical Commission) is responsible for basic electrical standards, IEEE and CIGRE provide technical guidelines, while national grid companies (such as Saudi SEC, UAE DEWA, Kenya KPLC) each issue their own grid connection specifications and equipment technical specification books. When Chinese general contractors "go global," they often face triple constraints: "Chinese national standard design habits + owner requirements for IEC/European and American standards + local mandatory regulations." In recent years, with the increase in power interconnection projects under the "Belt and Road" initiative, owners have increasingly tended to directly reference IEC standards in contracts while superimposing their own national grid guidelines, forming an applicable framework of "contract takes precedence, IEC provides the fallback, local regulations supplement."

In terms of scope of application, the substation construction discussed in this article applies to overseas EPC/PC general contracting scenarios, covering new construction, expansion, and renovation projects, with voltage levels mainly ranging from 66kV to 500kV, while also considering medium- and low-voltage distribution stations. It does not apply to special fields such as nuclear power dedicated substations or the DC side of converter stations.

II. Detailed Explanation of Core Content

2.1 Three-Tier Structure of the Standard System

The technical standards for overseas substation projects typically present a "pyramid" structure:

Tier	Content	Typical Source	Binding Force
Top	Contract technical specification, owner requirements	Owner/consulting engineer	Highest, executed with priority
Middle	International standards	IEC 61850, IEC 61936, IEC 62271, IEEE C37 series	Mandatory once referenced in contract
Bottom	Local mandatory regulations	Host country grid guidelines, building fire safety, environmental regulations	Mandatory by locality

Key Reminder: Contract technical specifications are often stricter than IEC. For example, some Middle Eastern owners specify GIS partial discharge levels and temperature rise limits higher than IEC 62271, and pricing and design must be based on these.

2.2 Primary Equipment Selection and Layout

Primary equipment includes main transformers, GIS/AIS switchgear, surge arresters, instrument transformers, busbars, etc. Core decision points:

• AIS vs GIS: GIS occupies less space, offers higher reliability, and is maintenance-free, but has higher cost; AIS has lower cost and is easier to maintain, but occupies more space. For overseas urban projects and dusty/salt-spray environments, GIS is preferred.
• Main transformer selection: It is necessary to clarify capacity, impedance, voltage regulation method, and cooling method (ONAN/ONAF/OFAF), and to verify transport limits—overseas inland projects are often forced to reduce capacity or use split transport due to road weight restrictions.
• Layout scheme: It is necessary to combine local seismic intensity, wind load, and ambient temperature. For example, Middle Eastern projects need to consider capacity derating at 50°C, while Southeast Asian projects need to consider high humidity and thunderstorms.

2.3 Secondary System and IEC 61850

The secondary system is the link where overseas projects are most prone to "pitfalls." IEC 61850 has become the de facto standard for digital substations, but implementation varies greatly:

• GOOSE/SV networking: It is necessary to clarify the network redundancy scheme (PRP/HSR) and switch brand compatibility.
• SCADA interfacing: The owner's dispatch master station protocol may be IEC 60870-5-101/104, DNP3.0, or IEC 61850, and the point table and communication protocol must be confirmed in advance.
• Protection settings: These must be reviewed by the owner's dispatch department. In overseas projects, the setting approval cycle often reaches several months and must be included in the schedule plan.

Checklist: Must-Check Items Before Secondary System Delivery

1. Communication protocol and point table confirmed in writing by the owner

2. Protection setting sheets approved

3. Cybersecurity requirements (such as NERC CIP-type requirements) satisfied

4. Time synchronization (GPS/BeiDou) scheme confirmed

5. Spare parts and special tools delivered

2.4 Civil Works and Interface Management

Civil works are often underestimated but are in fact a major source of schedule and cost risk in overseas substations:

• Foundation treatment: Overseas geological data are often incomplete, requiring supplementary investigation. Treatment schemes for soft soil, expansive soil, and saline soil affect cost.
• Structures and equipment foundations: These must strictly match the primary equipment manufacturer's data. Deviations in embedded parts can make equipment installation impossible.
• Interface management: Interfaces between civil works and electrical, electrical and communication, and station and line need to be managed with an interface matrix table, clarifying boundaries of responsibility.

2.5 Grid Connection Commissioning and Handover

Grid connection commissioning is the "final kick," and common problems in overseas projects include:

• The outage window approved by the owner's dispatch is limited, and the commissioning plan must be precise to the hour.
• Protection joint testing, telemetry and telesignaling verification, and AGC/AVC joint testing (if required) must be completed.
• Handover documents include as-built drawings, test reports, O&M manuals, and training records, none of which can be omitted.

III. Comparison with Other Standards

Comparison Dimension	Chinese National Standards (GB/DL)	International Standards (IEC/IEEE)	Local Standards
Design philosophy	Mature, relatively conservative, accustomed to coefficient method	Performance-oriented, allows engineering judgment	Mostly inherited from suzerain or regional standards
Typical standards	GB 50059, DL/T 5218	IEC 61936, IEC 62271, IEEE 80	Such as SEC, DEWA technical specifications
Equipment selection	National standard parameter system	IEC parameter system, requiring conversion	Often specifies brands or equivalents
Grounding and lightning protection	GB/T 50065	IEEE 80, IEC 62305	Local soil and thunderstorm data
Secondary communication	DL/T 860 (equivalent to IEC 61850)	IEC 61850	Owner dispatch protocol
Main differences	Larger margins, different drawing conventions	Greater emphasis on verifiability and documentation	Local approval and grid connection requirements

Practical Conclusion: One cannot simply "apply national standards" nor blindly "use full IEC." The contract should serve as the guiding framework, and a standard difference matrix should be created to close out each item one by one.

IV. Typical Application Scenarios

Scenario 1: Power Supply Works Supporting the China-Laos Railway

Along the China-Laos Railway there are multiple traction substations and distribution substations. Public reports indicate that the project adopted Chinese technical standards and equipment while also meeting Laos' local grid connection requirements. The experience from such projects is that the standards for traction stations and public substations need to be sorted out separately to avoid mixing them.

Scenario 2: Substations Supporting the Pakistan Matiari-Lahore HVDC Transmission Project

Under the China-Pakistan Economic Corridor framework, the Matiari-Lahore HVDC transmission project, including converter stations at both ends and supporting AC substations, involved Chinese participation in construction. Public information indicates that the project adopted a combination of IEC standards and the owner's grid connection specifications, with the interface between the secondary system and Pakistani dispatch being a key focus.

Scenario 3: Substations in Middle Eastern Gulf Regions Such as Saudi Arabia and the UAE

Gulf country grid companies have strict technical specifications, generally requiring GIS, high seismic resistance, and high-temperature derating, and they also have high requirements for document approval and factory acceptance testing (FAT). Multiple publicly reported projects undertaken by Chinese enterprises show that early involvement in studying owner specifications and locking in equipment suppliers are key to risk control.

V. Common Questions FAQ

Q1: The contract references IEC, but the owner also provides national specifications. In case of conflict, which prevails?

Usually the contract technical specification takes precedence, followed by the owner's specifications, and finally IEC. However, the priority clause must be clarified during contract negotiation; otherwise, disputes during execution will be significant.

Q2: Can Chinese equipment be directly used in overseas substations?

Yes, but IEC type test reports, CE or corresponding certifications must be provided, and the owner's specifications must be met. Some owners do not accept GB-only reports, so difference testing must be done in advance.

Q3: How should an IEC 61850 substation interface with the owner's legacy dispatch master station?

Protocol conversion devices (gateways) need to be added, and the point table and communication protocol must be confirmed with the owner in advance. It is recommended to complete a joint debugging scheme review during the design stage.

Q4: How long does an overseas substation project generally take?

New 66kV–132kV substations typically take 12–18 months, and those above 220kV take 18–30 months, depending on approvals, supply, and outage windows. Please refer to the actual project plan.

Q5: What should be done if the owner does not approve an outage window during the commissioning stage?

The responsibility for outage windows should be stipulated during the contract stage, and backup windows should be reserved in the construction plan. If necessary, bypass or temporary power supply schemes should be adopted.

VI. Practical Recommendations

1. Create a standard difference matrix during the contract stage: Compare contract specifications, IEC, and local regulations item by item, mark conflicts and priorities, and form written clarifications.

2. Lock in key equipment early: Main transformers, GIS, and protection devices have long lead times, so technical clarification and FAT plans should be completed as early as possible.

3. Involve the secondary system early: Confirm protocols, point tables, and setting processes with the owner's dispatch during the civil works stage to avoid later rework.

4. Tabulate interface management: Establish a civil works–electrical–communication–line interface matrix, clarifying responsible persons and deliverables.

5. Front-load local compliance: Assign dedicated personnel to track local requirements such as environmental protection, fire safety, construction permits, and personnel visas.

6. Deliver documents and training in parallel: Prepare completion materials, O&M manuals, and training records in the owner's format in advance to avoid handover delays.

7. Reserve buffer time for commissioning and grid connection: Overseas approvals and outage windows are uncontrollable, so at least 15%–20% buffer should be reserved in the plan.

8. Establish a dynamic list of standards and specifications: Owner specifications may be updated, so assign dedicated personnel to track them and assess the impact.

---

Note: The specific project information mentioned in this article is all from public reports. For specific standard numbers, contract clauses, and amounts, please refer to the project's official documents and contracts.