Nuclear power plants – Electrical power system – General requirements
|Publication Date:||1 October 2020|
|ICS Code (Nuclear power plants. Safety):||27.120.20|
• provides requirements and recommendations for the overall Electrical Power System. In particular, it covers interruptible and uninterruptible Electrical Power Systems including the systems supplying the I&C systems;
• is consistent and coherent with IEC 61513. Like IEC 61513, this document also highlights the need for complete and precise requirements, derived from the plant safety goals. Those requirements are prerequisites for generating the comprehensive requirements for the overall Electrical Power System architecture, and for the electrical power supply subsystems;
• has to be considered in conjunction with and at the same level as IEC 61513. These two standards provide a complete framework establishing general requirements for instrumentation, control, and Electrical Power System for Nuclear Power Plants.
This document establishes:
• the high level specification and requirement to implement a suitable Electrical Power System in a NPP that supports reactor systems important to safety. It also enables electrical energy production providing the transmission grid with active and reactive power and electro-mechanical inertia;
• the relationships between:
- the plant safety requirements and the architecture of the overall Electrical Power System and its sub-systems (see Figure 1) including:
a) the contribution to the plant Defence in Depth;
b) the independency and redundancy provisions;
- the electrical requirements and the architecture of the Electrical Power System and its sub-systems;
- the functional requirements and the architecture of the Electrical Power System and its sub-systems;
- the requirements associated with the maintenance strategy and the architecture of the Electrical Power System and its sub-systems;
• the design of Electrical power sub-systems (e.g. interruptible and uninterruptible);
• the requirements for supporting systems of Electrical Power System (HVAC, I&C, etc.);
• the Electrical Power System life-cycle framework.
This document does not cover the specification of:
• I&C systems;
• the transmission lines connecting to substations outside the NPP;
• electrical equipment requirements already defined in the industrial IEC standards;
• electrical power for security systems (e.g., fences, surveillance systems, entrance control);
• lighting and socket facility.
This document does not consider power production requirements.
NOTE Figure 1 is based on IAEA SSG34:2016, Figure 3, with adaptation regarding the scope.
This figure provides only an example. Various possible arrangements of buses, loads, generators and interconnections would meet the requirements of SSR-2/1. Furthermore, many elements of the plant system, such as buses that are not important to safety and direct current power systems, are not shown. This figure is intended only to represent the relationship between the elements of the plant power systems that are within the safety classification and the preferred power supply. The elements of the preferred power supply that are not within the bounds of the important to safety power supply are outside the scope of the plant safety classification. The system elements included in the important to safety power supplies will differ according to plant design and the classification methods applied in different States. The classification methods are held by IEC 61226. Some plant designs may not require safety standby power sources. All nuclear power plants are expected to have safety direct current power supplies.
Application: new and pre-existing plants
This document is applicable to the Electrical Power System of new nuclear power plants and upgrading or back fitting of existing plants.
For existing plants, only a subset of requirements may be applicable and this subset should be identified at the beginning of any project.
This document consists of six normative clauses (an overview is provided in Figure 2):
- Clause 6 addresses the identification of requirements;
- Clause 7 addresses the design of the electrical architecture;
- Clause 8 addresses the sub-system requirements;
- Clause 9 addresses the verification;
- Clause 10 addresses the overall integration and commissioning;
- Clause 11 addresses the overall operation and maintenance.
Interaction with level 2 standards
This document shall permit an electrical designer to establish the list of requirements applicable for the design.
It also provides the different provisions applicable for the different requirements.
These provisions will be applied to the different type of power networks (sub-system):
• interruptible AC power network;
• uninterruptible power network.
Moreover, other transverse level 2 standards will define requirements applicable to electrical architecture definition.
The nuclear standards linked with the safety provisions (such as safety classification, separation, qualification or surveillance testing, etc.) are considered as input data for this document.