Cathodic Protection Control from ETA Engineering

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ETA Engineering, Inc.

2010 E. University Dr. Suite 20

Tempe, AZ 85281

Phone: 480-966-1380

Toll Free: 1-877-964-4188

Fax: 1-480-966-1516

info@etaengineering.com

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Note: Prices are subject to change without notice due to changes in other vendors' prices to us. These changes may arise from normal product development plus fluctuations in foreign exchange rates and commodity prices.

Frequently asked questions (FAQ).

Introduction to Cathodic Protection

As the price of extending utility power lines has increased significantly, photovoltaics have become the preferred source of power in many applications, including Cathodic Protection.

Cathodic Protection (CP) works by impressing a current on a metallic structure that is in contact with the earth, such that the structure is maintained at a negative voltage (usually about -.85 to -1.1 vdc) with respect to a copper/copper sulfate half cell in contact with the earth. Cathodic Protection is used to protect pipelines, steel tanks, well casings, and even highway bridges.

Even large structures in contact with the earth can be protected with a reasonably sized system. A Cathodic Protection or Corrosion Engineer should be contacted to evaluate the application and to specify the ground bed type and dimensions along with the current and voltage requirements. A system should normally be sized for some future growth since protective coatings deteriorate further with age.

ETA Engineering Inc. has designed a family of Cathodic Protection Controllers that meet the majority of CP land-based applications. Normally powered with Photovoltaics, the systems range in output power from a few watts to 2 Kilowatts. Systems are available in nominal battery voltages of 12, 24, 48 Vdc with currents ranging up to 50 Amps. Systems may be paralleled for higher output currents by setting the controls to the constant current mode. We can supply complete systems except for the ground bed, anodes, field wiring, half cell (if used) and a shelter if used. The controller uses high efficiency components in a DC to DC "buck" converter topology that gives conversion efficiencies in the area of (95%). No rheostats or dropping resistors are used to lower the output voltage, thus saving the power dissipated in the traditional "rectifier" systems.

Our experience dates back to the late 1970's when the first systems were being designed and installed. In 1993 we redesigned the electronics to allow a positive ground system from the battery bank directly to the ground bed. This improves field installation by preventing "ground loops", and also minimizes lightning protection problems. The PV module frames and structures should be grounded, but the PV input cables left ungrounded. Leakage currents and static build-up are handled by the module frame grounds, and a diode drop into the positive terminal of the battery which is grounded. Lightning surge protection is provided by the PV regulators on the input side and the PV controller on the negative output side.

PV powered systems are normally designed for 5 to 10 days of autonomy (sunless days). The batteries are often protected by a low voltage cutoff which shuts down the controller before damage to the batteries occurs. As a PV distributor and control manufacturer you will find our pricing very competitive. Our systems usually require fewer PV modules due to the high efficiency of the ETA controller.

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Last updated: December 19, 2008

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