Synchronous condenser packages — solving the challenges of renewable energy integration

ABB Australia Pty Ltd
Monday, 02 November, 2020

Synchronous condenser packages — solving the challenges of renewable energy integration

ABB is a global leader in power and automation technologies that enable utility and industry customers to improve their performance while lowering the environmental impact. Synchronous condensers from ABB ensure efficient and reliable operation of power grids through reactive power compensation and additional short circuit power capacity.

Operating principles

A synchronous condenser is a device that supports network voltage by providing reactive power compensation and additional short circuit power capacity.

Fundamentally, a synchronous condenser is a synchronous generator operating without a prime mover. Generation or consumption of reactive power is achieved by regulating the excitation current.

An important benefit of a synchronous condenser is that it contributes to the overall short circuit capacity in the network node where it is installed. This, in turn, improves the chances that equipment connected to the network will be able to “ride through” network fault conditions.

A synchronous condenser is also well-suited to operating during overload duty for shorter or longer periods of time. Synchronous condensers can support the power system voltage during prolonged voltage sags by increasing the network inertia. They can therefore be utilized as VAR compensating devices in situations where voltage instability must be prevented at all cost.

Dynamic properties

As with any synchronous motor or generator, the electrical dynamics of a synchronous condenser are largely determined by the reactants of the condenser and by the nature of its excitation system. Low transient reactants and comparably high rotor inertia ensure high transient stability margins and excellent fault ride-through capability.

Synchronous condensers from ABB are equipped with a brushless excitation system which allows for considerable over-excitation (field forcing) in case of network contingencies. Excitation control is performed by an AVR which is tuned to match the requirements of the specific application.

ABB modular synchronous condenser solutions

ABB offers module-based synchronous condenser solutions with active components designed according to project-specific needs. This allows for a flexible product as well as a short time to in-service.

ABB synchronous condenser modules are compact and fully functional units, with minimal footprint on site and minimal need for external auxiliary support.

The ABB Modular Systems team has extensive experience supplying packages inclusive of the: e-Houses (Transportable Substation Buildings), associated HV & LV equipment, SCADA. Specialising in delivering coordinated & cost-effective product package solutions.

Components of the package

A synchronous condenser is a large rotating machine which is erected on a heavy foundation. Refer to technical specification (TS) and dimension drawings for details. It is usually transported as two pieces (machine + cooler top section). The Main Terminal Box (MTB) is always separately handled. Sleeve bearings are used with jacking oil pumps assisting start up.

An MTB contains Current Transformers (CTs) and Potential Transformers (PTs), protection devices such as arresters and surge absorbing capacitors, plus Neutral Earthing Resistors (NER). It is a sealed IP55 enclosure with pressure relief openings. In larger sizes, NERs are located in a separate ventilated compartment. Line side and Neutral side equipment are separated inside and large openings aid inspections and maintenance. Connection options are from the cables beneath or from the side busbar.

Pony motor

Synchronous condensers are started by a variable speed driven pony motor. It is directly coupled to the synchronous condenser shaft. Typical power ranges are approx. 200–1000 kW depending on rotating messes. Coupling and coupling guards are included.

A variable speed drive assists in managing acceleration time and aids the seamless synchronisation to the network. A frequency converter can be a wall mounted or floor standing unit. It is fitted with a communication card for controlled synchronisation by a Condenser Control Panel (CCP). The converter needs to be installed indoors in a container or prefabricated building together with several motor control centres (MCCs).

Lube oil unit

The lube oil unit should be located a few metres away from a synchronous condenser on a lower base. An oil return line must have a set slope of about 3 degrees. The unit may include an air cooler with an electric blower or a water cooling system. Redundant circulating pumps are always included with filters, temperature and flow monitoring.

Control and protection

Condenser control panel

A condenser control panel is the functional control unit of the synchronous condenser package. It is a floor standing cabinet which houses various instruments including:

  • Automatic voltage regulators (AVRs) with full redundancy
  • Protection relays (two different brands as per current requirements)
  • A Programmable Logic Controller (PLC), which controls and monitors all the built-in measuring instruments, signals and interface with the upstream control.

Cooling options

Fin-fan cooler

For outdoor installations in Australia a closed circuit water cooled synchronous condenser is the most common solution. The water is circulated between the radiator elements in the machine and the fin-fan cooler (FFC), where blowers are dissipating the heat to the surroundings. The blowers are PLC controlled subject to loading of the synchronous condenser.

Two versions are available. For smaller units the cooler is integrated on the top of the condenser (CAWA), which will save installation space. For larger units the FFC needs to be separate with its own control panel.

The most common cooling format is a machine with a top mounted air to water heat exchanger (CACW). This solution gives the highest power output. The heat exchanger is connected via external piping to the separate fin-fan cooler unit.

Integrated Water Cooler

This type of innovative cooler arrangement is an independent closed circuit cooling system (CAWA).

This smart cooler concept uses a water-to-air cooler, integrated on the top of the condenser’s air-to-water heat exchanger. It is designed specifically for the characteristics of the machine and offers a simple and compact solution resulting in significant space savings. This arrangement enables higher machine power compared with the CACA cooler system.

Air to air cooling system — alternative design

This machine mounted CACA (air to air cooler) with powerful blowers is speed controlled according to synchronous condenser loadings and cooling requirements.

This cooling format gives slightly less power output, but will result in a smaller footprint as no separate FFC unit is needed. The top mounted CACA cooler is larger than the actual machine body.

Image caption: Darlington Point Solar Farm Project. Credit: Edify Energy and Octopus Investments

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