Electricity is a fundamental service in the modern world, since it provides the fastest and most efficient way to deliver large amounts of energy. However, this energy delivery capacity also makes electricity dangerous if not handled properly. This is precisely what electrical engineering deals with - harnessing the power of electricity safely.
Electrical installations use much less space than mechanical and plumbing systems, but they are the backbone of many building services. A well-designed electrical installation can deliver an adequate voltage and power output for each device, while including protection measures against all types of electrical faults.
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Which Are the Types of Electrical Faults?
Among the general public, electrical faults and short circuits are viewed as equivalent concepts. However, there are other types of faults beyond short circuits, and the following are some examples:
A ground fault occurs when a live conductor touches an object or surface that is not part of the circuit.
A line-to-line fault occurs when two live conductors at different voltages touch each other.
An arc fault is an electric discharge that travels through the air.
An overload occurs when an electrical device draws current above its rated value.
These issues normally trigger an immediate response from electrical protection devices. However, there are other less severe conditions that cause damage in the long run. A common example is undervoltage, which occurs when a power system has a supply voltage below the rated value of the devices connected. In electrical systems with several phases, there can also be a voltage imbalance between phases.
How Electrical Engineers Prevent Faults
It is common knowledge that an exposed live wire represents danger. Electrical wiring is coated with insulation and introduced in conduit, providing two layers of protection. However, insulation can melt if a wire carries current above its capacity, and electrical engineers must ensure that the wiring sizes specified are enough for the expected current.
When a wire has adequate ampacity, insulation will not melt under normal operating conditions. If an electrical fault raises the current, electrical protection devices disconnect the circuit before the high current can cause damage.
Ground faults and arc faults are particularly dangerous: they can produce currents that are not high enough to damage wiring, but of enough magnitude to cause electric shock or to start a fire. In applications where these types of faults are a risk, electrical engineers specify ground-fault circuit interrupters (GFCI) and arc-fault circuit interrupters (AFCI).
The Importance of Optimal Wiring Capacity
When selecting wire, electrical engineers focus on finding the optimal ampacity depending on the application. Undersized wiring is dangerous because its insulation can easily melt, leading to an electrical fault. However, oversized wiring represents an unnecessary expense. Also consider that a higher current capacity does not result in improved safety:
If the wiring is oversized, there is no safety benefit because conductors are already protected by the circuit breaker.
On the other hand, if the circuit breaker is oversized, it may allow currents above the wiring capacity. In other words, an oversized breaker creates an unsafe condition.
If both the wiring and the breaker are oversized, the devices connected to the circuit are not protected from overload. For example, if the wiring and circuit breaker are both sized for 50 amperes, an appliance with a rated current of 10 A is not protected effectively.
In a few words, an electrical installation is safe when the capacities of wiring and circuit breakers are optimized. Both oversizing and undersizing have negative consequences.
When energy efficiency measures are deployed, it may be possible to specify an electrical installation with reduced wiring capacities. Safety is not compromised in this case, since the current drawn by electrical equipment is lower.
A well-designed electrical installation is also a safe installation. When you work with qualified electrical engineers, they perform a detailed analysis of all electrical loads and the possible fault conditions, to specify suitable conductors and protection devices.
Professional electrical engineering services also guarantee code compliance, ensuring a quick project approval. To minimize fire risks, electrical installations should be designed according to the NFPA 70 National Electrical Code (NEC). Also, the components specified should have certification marks from a Nationally Recognized Testing Laboratory like UL or ETL.
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