What is power systems analysis?
Power System Analysis involves looking at an existing or proposed power system and ensuring that it is suitable, stable and resilient. The majority of the UK’s power system is connected to form a grid, broadly divided into the transmission and distribution networks.
Power Systems Analysis involves not only looking at system stability and resilience for existing system, but also the impact of connecting a new system. Each new system must be added safely without compromising system stability (for example a grid connection compliance study). This involves:
Safety and risk
It is important to ensure that the equipment remains serviceable for normal and abnormal (transient) conditions, e.g. a fault, switching surge or lightning strike. Equipment is designed to tolerate some extremes in system characteristics for a short duration, however, there are limits. Part of the assessment is to ensure that these limits determined by the manufacturer are not exceeded. If presented with an abnormal event, we also need to ensure that the equipment and surrounding area is safe for human occupation. This is where Protection coordination, Earthing and lightning protection comes in.
System limitations
A generation site may be required to operate over a range of voltages and power factors at the connection point. We need to determine any system limitations and advise on whether mitigation or compensation is required.
Normal / abnormal system conditions
The power system must remain operational and compliant with network requirements for both normal and abnormal system configurations. For example, if there is an outage in the wider network, resulting in a slight change in the electrical characteristics at the connection point, would the new system remain compliant?
Identifying system weaknesses
Whilst we offer system design services, occasionally our team will be given a design to review/validate. In this case we would assess each of the design from transformer or switchgear specification to ensuring that the amount of generation or storage is suitable for the desired connection capacity. Our experience allows us to predict potential issues before they transpire.
Ensuring system can operate from a black start or independently from the grid
Unfortunately, grid outages do occur. Depending on the type and priorities of the system, it may need to operate independently for a while prior to re-synchronising to the grid post outage. Some sites are even important for restoration of the grid and must therefore be able to start independently. PSE 2 can create or work with detailed system models including generator dynamic models that would exhibit the same behaviour as the actual generator or inverter (digital twin). These digital twins allow us to assess stability for a wide range of system conditions.
What is a power system?
There are three main types of power system. They are:
- Generation: this type of system generates power. As an export of power it includes gas engines, power stations, nuclear power, renewable energy, and tidal schemes.
- Distribution/Load: this type of system imports power, it relates to any system that does not have its own internal generation of power such as industrial sites, data centres, residential areas and commercial supplies.
- Storage: this type of system stores power (including battery, flywheel, pumped). Storage, particularly Battery Energy Storage Schemes (BESS) are becoming more common and are being used to compliment renewable energy source. This starts to alleviate the problem of renewable energy availability (e.g. due to lack of sun or wind) as energy can be stored when not required and utilised when it is required.
What are the components of a power system?
Depending on the need for the system and the types of power it is generating, the power system will be made up of components including:
- Transformers
- Cables
- Overhead lines
- Switchgear
- Relays and communications
- Generators
- Inverters
- Batteries
- Measurement devices
How does PSE 2 carry out a power system analysis?
The first stage would be to send the client a request for information (RFI) including a list of information required to carry out the required studies. This RFI will allow us to filter the relevant data and request any information that’s missing. Sometimes data is unavailable, that is where PSE2’s experience comes in and realistic assumptions can be made if necessary.
As soon as we have the data, we will conduct the relevant simulations and produce a report with our findings to the customer; often with a follow up meeting to discuss any questions or issues. Following this if any modifications are required we would work through each issue and discuss a plan to review the document. We may need to repeat elements of the study until all requirements are met and everyone is happy.