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Making wind power more reliable

Application of a UPS within a Wind Power Substation

The Scenario

Newfoundland and Labrador Hydro in conjunction with NewWind Group Inc. partnered to install a 27-megawatt farm in St. Lawrence featuring nine, three-megawatt wind turbines that generates roughly 100,000-megawatt hours a year – enough to provide electricity to approximately 6,800 homes.

Successful operation and protection of the wind farm substation requires reliable operation of the protection and control systems. The protective devices are used to detect faults on the network and operate circuit breakers to isolate any faults. Tripping and re-closing of substation breakers in a fault situation is a common mode of operation. Rapid fault detection and isolation is a requirement for connection to the grid avoiding cascading failures or complete loss of the grid network; thus the need for an AC & DC UPS system.

The Challenge

In the spring of 2008 Reliable Power Systems Inc responded to a RFQ to supply and deliver an indoor inverter and battery/charger system to support both the DC & AC loads.

The 125volt DC loads consists of:

  • Substation circuit breaker
  • Protection relays
  • Substation SCADA (Supervisory Control and Data Acquisition) system

The 125volt AC loads consists of:

  • Telecommunication equipment
  • Lighting circuits
  • Vestas wind turbine SCADA Systems

The Solution

After reviewing the application requirements with contractor the contract was awarded to supply the following material:
HV Series Uninterruptible Power Supply (UPS) System
Marathon VRLA (Valve-Regulated-Lead-Acid) batteries

The UPS system is a line interactive design incorporating an IGBT based microprocessor controlled PWM inverter, high speed transfer SCR devices, constant voltage regulating transformer and battery charger. The UPS provides complete load immunity from all line disturbances and power interruptions with no loss or disruption in AC output power.

This solution was proven to be the most cost effective while offering a standard of-the-shelf well proven and tested design. The rugged HV Series UPS operates on a nominal 120vdc buss. The 20-amp internal charger provides rapid recharge current to the batteries while providing the “standing” DC Loads of approximate 5 amps. The HV Series AC output rating of 14,000va/10,000watts provides more than ample power to the substation AC loads.

The Marathon battery plant is made up of two separate strings of ten 12volt (10 x 12 = 120vdc) battery modules. The two strings provide redundancy and are mounted on the same rack. These M12V125F batteries provide high performance and reliability. The front positive and negative terminals; greatly facilitates both installation and maintenance.


In August of 2008 the UPS module and battery banks were successfully commissioned and tested on-site by Reliable Power Systems Inc. For more information about this application please feel free to contact our office anytime.