Why Power System Protection is Important Aspect of the Grid?

Introduction

Power system protection is the backbone and security assurance of the complex electricity grid that powers our modern world, from homes and businesses to industries and infrastructure. But what happens when a fault or disturbance occurs in the power system? Electrical faults can cause severe damage, equipment failure, and even widespread blackouts without proper protection. The downside of failures is catastrophic across all endeavors of our lives. This is where Power System Protection plays a crucial role in maintaining the electrical grid’s stability, safety, and reliability.

This brief post will explore why power system protection is crucial, the key components used, and how it improves grid security.

What is Power System Protection?

Power system protection allows the grid to detect disturbances or faults and isolate them as fast as intended. Like any other system, the electric grid is imperfect and has vulnerabilities. Several natural events or human-related actions are sources that lead to faults. These natural events include lightning strikes, heavy rains, floods, and bushfires (which could also be caused by human actions).

Human errors or negligence (errors in design, programming, or operational mistakes) can also cause faults in the power grid. Moreover, aging electrical components or repeated operations can lead to failures.

Nonetheless, whether persons or natural events cause faults, protection devices are installed to monitor the condition (24/7) of the grid continuously. In the scenario where a failure is found, the unhealthy portion is expected to be quickly isolated, leaving the healthy part intact for continuity of service.

Protection of the Grid is a Fundamental Need for Security

Grid protection is one of the most critical aspects of the electrical and power industry. It is fundamental to the electrical infrastructure’s reliability, stability, dependability, and security. Protection is the “last line” of defense for the electrical grid.

But could the power grid be operated without protection? The answer is simple, and almost all engineers and industry stakeholders will largely agree on the need for protection. It is one that we can’t compromise. Technically, an electrical circuit could function without protection. However, who will ever want to drive a vehicle without a braking function or any safety measure when other factors could result in danger on the road?

No one expects an accident while driving, but personnel safety and machine reliability are crucial aspects of vehicle design.

Hence, a power system without protection will never meet compliance standards and regulations for operation. This means grid protection is critical and should be treated as such.

Why is Protection so Important?

As stated above, the importance of power system protection is obvious and can’t be underestimated. Some merits of protecting the grid are:

Grid Protection Prevents Equipment Damage

Whenever there is an electrical fault, a lot of current flows through various grid components. This can overheat and destroy critical equipment such as transformers, cables, conductors, and circuit breakers. Therefore, protection systems help prevent costly damage by quickly isolating faulty sections before they cause catastrophic failure.

Ensures Reliable Power Supply

A well-protected power system ensures electricity remains available even if a fault occurs. Reliability is achieved by isolating only the faulty section, preventing unnecessary blackouts and keeping the rest of the grid functional.

Protection Enhances Safety

One of the most important functions of protection is ensuring the safety of personnel working or living near electrical infrastructures. Uncontrolled electrical faults can lead to fires, explosions, and electric shocks, endangering lives. Protection devices like relays, circuit breakers, and fuses help eliminate such risks.

It Reduces Financial Losses

Homes and businesses rely on a continuous electricity supply for various survival processes. A loss of power leads to disruption resulting in substantial financial losses for businesses, industries, and utility companies. Proper protection minimizes downtime, ensuring continuous operations and economic stability.

Protection Supports Grid Stability

Faults can spread rapidly in an interconnected power network, affecting multiple regions. Failure to remove any fault in a part of the grid leads to a cascading effect that runs through the undisturbed areas. Protection systems ensure faults are cleared as fast as possible (by design), preventing disturbances from escalating into significant grid failures.

Electrical system protection is fundamental to grid security, reliability, stability, and dependability.

Major Components used in Grid Protection and their Function

How is power system protection achieved? The grid is protected using several devices, each playing a unique or specific role(s) for a collective protection application.

In simple terms, protection ensures the grid operates within its boundaries for normal system operating parameters (like current, voltage, and frequency). As mentioned earlier, faults lead to changes in normal operating conditions.

When we protect power systems, we prevent overcurrent, overvoltage, undervoltage, over/underfrequency or overloading conditions that could eventually lead to distressing scenarios.

Some major components used in protection are:

Instrument Transformers

Current transformers (CTs) and voltage transformers (VTs) are collectively referred to as instrument transformers. The current transformer changes a higher current to a lower current. For instance, a 1000A current flowing through a circuit has to be measured for protection or metering applications.

However, besides safety concerns, this 1000A is too high for any typical protective device or metering device to handle. The current transformer therefore transforms the 1000A (primary) to say 5A or 1A (secondary). The 5A or 1A is consequently fed into the protection device. The relay measures the 5A or 1A (at its input) but converts to the primary current (actual field current) by the CT ratio.

For a 1000/5A CT, the ratio will be 200. So, if the field current is 800A, the secondary current input to the relay will be 800A/CT ratio = 800A/200 = 4A. However, the relay’s current displayed (on screen or ) will be 4A × 200 = 800A.

The same applies to voltage. For example, a system at 145,000 V is too high. Therefore, having protective devices with insulation that could handle high voltages becomes uneconomical or unfeasible. As such, the 145,000 volt primary is transformed with voltage transformers (VTs) to 110 volt. This 110 V is fed to a protection device for application.

So, CTs and VTs measure electrical parameters (current and voltage) and provide data for protection relays.

Relays

Relays are the brain of the power grid. They continuously monitor the grid’s current, voltage, and frequency. These intelligent devices detect abnormal electrical conditions and trigger circuit breakers to isolate disturbances based on programmed settings.

Circuit Breakers

Circuit breakers are devices that interrupt the flow of current in circuits. They can be automatically or manually operated. A circuit breaker (CB) opens circuits to stop excessive current flow, preventing equipment damage. A protective relay senses the fault and sends a trip command to the circuit breaker to open the circuit. A close command can also be sent from the relay to close the circuit after the fault is cleared and standard conditions are sustained.

Fuses

Fuses are protective devices that interrupt circuit continuity. They melt under excessive current, cutting off power to prevent damage to circuit components.

How does Protection Work?

Video credit: Visual Electric

Summary

In a nutshell, the electrical grid is the stem of every economy, without it, we are retarded to the stone ages. To ensure that this critical infrastructure continues to perform optimally for the success of our homes and businesses, the grid must be reliable and secured.

Protection systems must be implemented to achieve a resilient, robust, dependable, and secured grid.

Protection systems monitor the operating conditions of the grid (24/7) and decide to isolate unhealthy portions as fast as possible, as it has been designed. Failure to do so may cause devastating conditions, leading to safety problems, equipment damage, and substantial financial losses.

In conclusion, protection is the last line of defense for the power grid. In a later post, we will discuss specific protection applications such as overcurrent, distance, differential, etc.

What do you think about power systems protection?

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