Low Cost Environmentally Safe Lightning Protection
Featured Product from Sankosha U.S.A., Inc.
Windfarms - Grounding with SAN-EARTH
Wind turbines are located in open spaces often in rocky mountainous areas where soil resistivity is high making them particularly vulnerable to lightning currents that may threaten human life or damage expensive equipment.
Partnered with surge protection devices (SPD’s), a low resistance path to earth is the most important factor in providing protection for both personnel and equipment. The best SPD’s available will fail to offer the required protection if grounding resistance is high, but designing an effective grounding system for single turbines or entire windfarms in a high resistivity environment or where space may be limited poses a serious challenge.
SAN-EARTH conductive cement offers a safe economical long term solution to the windfarm grounding problem. It was specifically developed for locations where resistivity is high and access might be difficult. The typical recommended design for a SAN-EARTH electrode system for a single wind turbine is shown below. It consists of a perimeter ground totaling 60 m (197 ft.) in length combined with four radial electrodes 30 m (98 ft.) each in length and yields a resistance value of 2.5 ohms in 300 ohm-meter soil. The SAN-EARTH electrodes are 0.25m (10 inches) wide and installed at a depth of 1 m (39 inches).
In higher resistivity environments often associated with wind farm installations, similar low resistance values can be achieved by simply increasing the length of the radials. Four 75 m (246 foot) SAN-EARTH radials yield a resistance of 2.4 Ω in a 500 Ω-m resistivity environment. Installation is relatively simple. First, 0.25 m (10 inch) wide trenches are dug to an appropriate depth, one meter in the examples here. SAN-EARTH can be installed as a dry powder or mixed with water and applied as a mortar. The counterpoise wire is placed in the trench so that it is surrounded by the SAN-EARTH material. Over time SAN-EARTH hardens to become a conductive solid. Thus, the surface area of the grounding electrode is greatly increased and lower resistance values are achieved. Corrosion in the counterpoise wire is prevented and conductor theft becomes much more difficult.
Wind turbines grounded in this way can be connected together to achieve even more dramatic results. In the example below, the grounding electrode systems for three turbines are connected together using the SAN-EARTH design. Vertical ground rods, often difficult to install at wind farm locations, are not needed to achieve a consistent low resistance connection to earth.
Wind turbine grounding systems must be designed so that excessive overvoltages are prevented and potential gradients that may cause damage to equipment or threaten human life are eliminated. With SAN-EARTH, that goal can be achieved easily and economically.
Grounding resistance and soil resistivity are, by definition, always proportional. Knowing that, we can see that the system above would yield a resistance value of 1.32 Ω in a 1,000 Ω-m resistivity environment. Even if the resistivity went as high as 3,000 Ω-m, this design would produce a resistance value below 4 Ω.
Manufactured in the U.S.A., SAN-EARTH is ideal for use in areas where soil resistivity is high. SAN-EARTH reduces construction costs and produces long term consistent results. It is environmentally safe and conforms to IEC Standard 62561-7.
Sankosha U.S.A., Inc.
For over 75 years, Sankosha has developed and manufactured the Ceramic Gas Tube Surge Arrester (Gas Discharge Tube or GDT). Sankosha gas tube arresters protect personnel, equipment and circuitry from abnormally high voltages caused by lightning or electrical transients. Our surge protection devices have well defined surge-limiting characteristics enabling them to spark over (or breakdown) when the abnormal voltage on a line reaches a specific level. When sparkover occurs in the GDT, the surge is redirected to earth.
Sankosha’s gas tube arrestors are known for their quality. Throughout the world, products from our factories provide protection for equipment and personnel. Sankosha has been selling gas tube arresters in the U.S. since the seventies and Sankosha U.S.A., Inc., the company’s 100% owned subsidiary, was established in 1987 to better service the growing market in the Americas.
Different applications require different surge suppressors and Sankosha provides gas tubes to meet every need. Consumer electronics, modems, satellite, computer, CATV/Broadband, industrial, and telecom circuit protection are just a few areas that utilize our gas discharge tubes. Sankosha’s gas discharge tubes are extremely durable and provide the industry’s best impulse life specifications. They feature high surge ratings with very low capacitance and provide excellent response to fast rising transients.
Sankosha gas discharge tubes are available in axial leaded, radial leaded, surface mount, and special packages. High voltage gas tube models like the Y08SV-312B are designed for power supply applications where HiPot testing is required, and we also manufacture very small gas tube arrester models for surface mount applications where real estate is at a premium. Sankosha’s GDT’s come in both two and three electrode configurations. Discharge voltages from 75V to 6000V are available.
Sankosha’s RJ45 LAN SPD provide reliable surge protection of GigE (1000Base-T), 100Base-TX, 10Base-T and Power Over Ethernet (PoE) equipment. All four compact Local Area Network modules are equipped with RJ45 Connectors and can be used as stand alone surge protection devices. They are also designed with integrated clips for easy installation on a standard 35mm DIN rail.
In the 1970’s, Sankosha developed SAN-EARTH, the original conductive concrete groundbed. SAN-EARTH M5C is a fine powder used to build highly effective environmentally safe permanent grounding electrodes. SAN-EARTH M5C is manufactured in accordance with Sankosha’s ISO 9001 Quality Standards and conforms to IEC Standard 62561-7 which specifies the requirements and tests for earthing enhancing compounds producing low resistance of an earth termination system. Safe, economical and permanent, SAN-EARTH is the best grounding solution for both equipment performance and personnel safety.