Electrical Design Considerations for Geothermal Power Plant

Geothermal energy is a proven source for direct heat and power generation. And, its source of energy is the earth that utilizes steam to produce electricity. And, hence the steam that comes out from hot reservoirs found inside the ground is at a depth of more than 80 km or 300-3000 meters. Therefore, the placement of the geothermal plant is around the steam field location. Such locations are generally known as geothermal fields.

Geothermal power plants are recommended to be cited in the chemically hostile environment. The design and planning of the electrical system for the geothermal plant comprise a generator, switchgear, power transformer, control system, instrumentation, and protection system. It requires much more attention during the design phase, especially to the transmission line system and the effect of stability on the existing network system.

Let’s dive in deeper to understand the electrical planning and design requirements for the geothermal power project:

The high-voltage power cables are directly buried underground, which carried heavy currents that generate heat in the wires. The heat produced must be dispelled adequately in the surrounding ground to avoid cable damage.

The earthing system for geothermal power stations should be designed correctly to enable electrical equipment protective devices to operate appropriately. It also makes the site safe for people under electrical fault systems and eliminates dangers.

One of the potential issues is the corrosion of bare copper electrical equipment from contamination of hydrogen sulfide present in the geothermal fields. Corrosion-resistant materials such as aluminum and stainless steel can help to avoid electrical equipment problems. Also, the use of heat shrink material on exposed copper, tinned copper wires, and careful selection of sealing gaskets and paint systems can help overcome corrosion problems.

Also, indoor electrical equipment such as printed circuit boards, protection, and instrumentation system are vulnerable to corrosion and failure. Solutions to overcome this problem includes the Specification of H2S rated instruments and connections, gold plating on printed circuit board connections, Provision of control cubicles with anti-condensation heaters, controlling the temperature and humidity, and inserting all sensitive equipment in a definite pressurized and H2S filtered room.

The widely used insulation material for power cables is Cross-linked polyethylene (XLPE). If the wires are placed in poorly drained cable trenches or directly buried underground wherein, H2S could accumulate and dissolve in rainwater surrounding the cables. The aluminum conductor is used to ensure that the power cables are mounted in the air-ground level.

Transformers exposed to the outdoor environment can be damaged or can operate improperly if the situation is corrosive or is otherwise contaminated. Nowadays, a modern high voltage circuit breaker contains Sulphur Hexafluoride (SF6) pressurized type, which is denser than air, inert colorless, and odorless gas. Hence, SF6 does not decompose or break down if released into the environment.

To conclude, for the successful completion of the geothermal power generation project, it is necessary to include inputs of electrical engineering during the initial planning stages. Then, detailed design and site supervision aspects must be taken into consideration, along with Civil, Mechanical, and Chemical engineering inputs. If you’re looking to develop or optimize electronic equipment or design an electrical system, you can consider hiring an electrical engineering design services provider to manage the power system requirements of your geothermal power plant.

Judith Morrison is an expert in the field of industrial engineering and writes articles related to piping, civil, equipment engineering related articles.