Switchgear is essentially a key component of electric utility transmission and distribution systems. This device consists of switches, fuses, circuit breakers, and other parts that protect, separate, and control electrical equipment. Switchgear acts as a collective centralized piece of equipment in extensive industrial and commercial facilities. Switchgear plays a significant role in protecting electrical equipment and averting hazards. It is not unusual to find medium voltage switchgear in major industrial setups.
What is Medium Voltage Switchgear?
The very purpose of switchgear is to switch, protect and control the circuits. Switchgear units are automated protective devices that can quickly close the trip circuit in case of a fault. Without switchgear, excessively heavy loads of electricity can pass through the circuit and cause damages. Switchgear can selectively shut off the faulty section of the circuit and allow power to keep flowing to the healthy sections. In turn, this also keeps the connected devices safe in case of electrical faults. Based on the requirements, the industry can use a highly secure unit such as an arc flash switchgear or one with regular safety features that are effective too.
How Does Medium Voltage Switchgear Work?
Medium voltage switchgear works by combining several components that protect circuits, manage power flow, and ensure safety. Here’s a basic overview of its operation:
- Power Distribution: The electric power from the utility is brought into the switchgear system. The busbars distribute this power across various circuits and components.
- Fault Detection: If there is a fault in the system, such as a short circuit or an overload, the circuit breaker detects the abnormal condition. The breaker then interrupts the power supply to the affected circuit, isolating it from the rest of the system to prevent damage.
- Isolation for Safety: If maintenance is required or if isolation is necessary for safety, the disconnectors are used to physically separate sections of the electrical network. These isolators ensure that no current flows during maintenance, preventing electrical hazards.
- Monitoring and Control: Throughout the process, the monitoring and control systems track the operation of the switchgear. This includes monitoring for faults, overloads, or abnormal conditions and providing alerts to operators. Advanced protection relays ensure that the switchgear reacts in real time to prevent further damage.
Ensuring System Integrity: In addition to protection against faults, medium voltage switchgear ensures the integrity of the entire electrical system by providing efficient power distribution. The switchgear ensures that electrical power is delivered where needed while keeping the system balanced and operational.
Components of Medium Voltage Switchgear
Medium voltage switchgear is made up of several key components that work together to ensure proper functioning and safety. Here are the main components:
- Circuit Breakers:
The circuit breaker is the heart of medium voltage switchgear. Its primary function is to interrupt the electrical current in the event of a fault (such as a short circuit) or an overload. The circuit breaker detects an overcurrent situation and, within milliseconds, trips to isolate the faulty section from the rest of the system. This prevents damage to electrical equipment and reduces the risk of fires or further faults. - Disconnectors:
Disconnectors, or isolators, are used to completely isolate sections of the electrical network for maintenance or emergency purposes. Unlike circuit breakers, which automatically open when a fault occurs, disconnectors are manually operated. Their purpose is to ensure that no current is flowing through the circuit during maintenance, providing a safe environment for technicians. - Busbars:
Busbars are metal conductors (usually copper or aluminum) that distribute electrical power within the switchgear. Busbars act as a central hub where power is distributed to various circuits, breakers, and transformers. They are designed to carry large amounts of current and ensure that the distribution of power remains balanced across the system. - Fuses and Protection Devices:
Fuses and protective relays play a crucial role in detecting faults in the system and preventing damage to the electrical equipment. Fuses provide a quick, low-cost method of protection by melting when excessive current passes through. Protection relays, on the other hand, are more sophisticated and can detect faults based on current, voltage, or frequency, sending a signal to the circuit breaker to trip when necessary. - Control and Monitoring Systems:
Medium voltage switchgear is often integrated with advanced control and monitoring systems. These systems allow operators to monitor the status of the switchgear in real time, ensuring that the equipment is functioning as expected. Control systems also allow operators to remotely operate the switchgear, switch circuits on and off, and perform diagnostics if needed.
What are the types of medium voltage switchgear?
Different applications require different technologies and protective measures. This calls for various types of switchgear units. Some of the key types of medium voltage switchgear are:
1. Arc Resistant Switchgear
Arc flashes from major electric faults result in a tremendous surge of power thatregular switchgearmay not be able to contain. An arc flash switchgear has the ark flash energy and diverts it away from the operator through a plenum. Ultimately, it releases the energy in an open area such that the energy would not cause any harm.
2. Vault or Subsurface Switchgear
This type of switchgear lies under the surface but allows the users to operate from above ground. The locations where this type of switchgear is applicable can either be dry or subject to water ingress. Vault switchgear uses SF-6 gas, solid materials, and solid-dielectric-in-air technology for insulation. Vacuum interrupters help to separate faults and protect the loads.
Also Read: Arc Flash Switchgear: How Does It Show Effectiveness in the industry
3. Metal-clad Switchgear
Metal-clad switchgear refers to a type of switchgear unit where separate metal compartments enclose components such as the main switch or circuit breaker, instrumentation, incoming bus, outgoing bus, etc. This type of switchgear is relatively popular due to the safety features and the ease of maintenance it comes with.
4. Metal-enclosed Switchgear
This switchgear comes with various safety features, such as circuit breakers, fusible switches, and power fuses. These devices usually stay in common compartments, together with the metering and control equipment. Metal-enclosed switchgear finds application in commercial as well as industrial setups.
5. Pad-mounted Switchgear
Pad-mounted switchgear is helpful in the case of systems that lie underground. This outdoor-rated and tamper-resistant switchgear uses vacuum interrupters, fuses, and switches to reduce the chances of outages, separate faults, and protect loads. This type of switchgear finds application in feeder sectionalizing, utility distribution, and circuit protection.
Essentially, different types of medium voltage switchgear offer varying levels of protection and come with their unique features. Leading brands like Solution Controls manufacture various models of switchgear, including arc flash switchgear for applications that require high levels of protection from arc flashes.
Also Read- Understanding the Use of Electrical Enclosures in the Industry