Angle DC

Angle-DC demonstrates a novel network reinforcement technique by converting an existing double 33kV Alternating Current (AC) circuit to Direct Current (DC) operation. It will be the first Medium Voltage Direct Current (MVDC) link in Europe and one of the first tests to convert circuits from AC to DC operation. The conversion will change the voltages from 33kV AC to ±27 kV DC.

Challenge

Angle-DC seeks to use an existing AC link between the isle of Anglesey and North Wales, where uncontrolled power flows are forecast to exceed thermal limits of the cables and overhead lines. The link will also provide extra capacity for the integration of renewable generation connecting to the island’s distribution network.

Scope

  • Trial the first flexible MVDC link in the Great Britain (GB) distribution system;
  • Trial conversion of an AC circuit to DC operation to enhance circuit capacity;
  • Control of power flows and voltage in the distribution networks using the MVDC link;
  • Assess the impact of conversion on the circuit cables and OHLs by monitoring before, during and after conversion using a trial Holistic Circuit Condition Monitoring (HCCM) system;
  • Provide real-life data on the cable ageing mechanism;
  • Development of  technical guidance, recommendations and policy documents for planning, procurement, operation and control strategy of MVDC converters and MVDC links;
  • Stimulate the a supply chain and stimulate a competitive MVDC market;
  • Bridge the gap between the  transmission network and low voltage distribution DC technologies;
  • Explore the feasibility of MVDC technology as an enabler for the Distribution System Operator (DSO) model;

Benefits

  • Increased capacity of the existing circuit without cable and line reinforcement;
  • Greater precision in the control of power flow through the circuit;
  • Active control of voltage at either end of the circuit;
  • Active control of reactive power flow at the end of the circuit;
  • Active control can result in lower losses in the distribution circuit;
  • Due to active control and increased power capacity, renewable energy connections to the distribution grid will be accelerated.

Frequently Asked Questions

Frequently Asked Questions

What is project Angle-DC?

What is project Angle-DC?

Angle-DC demonstrates a novel network reinforcement technique by converting an existing 33kV AC to DC operation. It would be the first MVDC link in Europe and one of the first test in converting from an AC to a DC circuit at 33 kV. This technique is expected to be an efficient solution to create network capacity from in-place assets. 

Why do we need Angle-DC?

Why do we need Angle-DC?

Angle-DC seeks to use an existing AC link between the isle of Anglesey and North Wales, where uncontrolled power flows are forecast to exceed thermal limits of the cables and overhead lines (OHL). It would also provide extra capacity for renewable generation connecting on the Island. 

What are the main problems Angle-DC is trying to address?

What are the main problems Angle-DC is trying to address?

The main targets areas that Angle-DC seeks to improve are:

  • Changing Networks - Increasing demand growth and uptake of distributed energy resources are placing pressure on the distribution network;
  • Reinforcement Wayleaves - Creation of new way-leaves for additional distribution circuits and substations is difficult and time consuming in the UK;
  • Passive Networks - The passivity of the distribution network  cannot satisfy future network requirements;
  • Network Segregation - Power exchange between two distribution networks is mostly only possible through primary grids. This can lead to higher networks losses.

Who are involved with the project?

Who are involved with the project?

The project is owned by SP Energy Networks. Cardiff University has been selected as the Academic Partner. Companies leading the HVDC market are also expected to be an important part of the project.

What is the duration of the project?

What is the duration of the project?

The project duration is 4 & 1/2  years, from January 2016 to April 2020. The project mainly comprises two stages, conversion stage and trial operation stage. The MVDC link is expected to be connected in early 2019. The operational stage analysis will test the link for real-operation use and how it affects the original AC OHL and cables.

What technology is Angle-DC using?

What technology is Angle-DC using?

ACDC converter technology provides a better use of the cables, improving the capacity of an AC link. It also provides a better power and voltage control, reducing the losses in the line and increasing the efficiency of the link. The MVDC converters will be based on Voltage Source Converter (VSC) technology, most likely using a Modular Multi-level Converter (MMC) topology

The Holistic Circuit Condition Monitoring (HCCM) allows us to know the ageing and real time state of the converted lines and cables. The technology provides a better understanding of the circuits, reducing faults and increasing the effectiveness of maintenance.

Where is Angle-DC being trialled?

Where is Angle-DC being trialled?

The conversion of the AC circuit will be between the isle of Anglesey and North Wales, across the Britannia Bridge. 

What does MVDC mean?

What does MDVC mean?

Traditionally electricity flows as AC; a sinusoidal wave with a frequency of 50Hz. During each cycle, the electricity is positive; it reduces to zero and turns to a negative minimum value and then returns to a maximum positive value again; starting a new cycle.

Thanks to the development of power electronics since 1960, DC transmission and distribution has come back to the electricity industry. DC always operates at a steady voltage, rather than cycle from positive to negative, which equates to more power being carried than in each cycle. DC converters can be actively controlled, improving power management of the network.

What does real-time Holistic Circuit Condition monitoring mean?

What does real-time Holistic Circuit Condition monitoring mean?

This approach will be used to give an indication of Partial Discharge (PD) based cable and OHL degradation and how this degradation trends over time. MVDC design parameters influencing PD degradation including: voltage ramp up/down, over voltages and ripple from power converters will be assessed.

Data will be analysed and benchmarked to provide information on the way distribution circuits are affected following DC conversion. 

What are the benefits of Angle-DC?

What are the benefits of Angle-DC?

The use of DC technology will bring a number of benefits to the operation of the distribution network and hence to the consumer as outlined in the following:

  • Enhanced power flow through an existing circuit;
  • More precise control of the flow of power in the distribution circuit;
  • Prevents the possibility of overload of the circuit;
  • Control of voltage at either end of the distribution circuit;
  • Control of reactive power flow at both ends of the distribution circuit;
  • Lower losses in the wider distribution network due to the improved voltage control;
  • Rapid support to the system voltage during faults;
  • Fault level decoupling between distribution systems;
  • Facilitating accelerated access to the network for renewable connections.

Reports & Documents

Events

Events

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