The 'Case' for a Case Study

On Wednesday 16th February 2022, the island of Trinidad experienced a major nationwide blackout due to a fault at one of the local utility's 220kV substations. The island of Tobago was unaffected. The fault occurred at 12:52 pm and power was eventually restored around 1:00am.

There have been several conjectures being postulated, many of which are non-technical and based in fundamentally flawed logic and reasoning.?

As such, it is imperative and prudent that a case study be done to review the following items as a minimum:

1. The sequence of events that led up to the blackout scenario

? Data from operators, DCS Historians, alarm registers, and other similar sources would be beneficial.

? There may have been leading indicators that signaled the emergence of a disturbance.

2. Details surrounding the nature of fault occurred. As a minimum this may include:?

? Exact source of the fault and which equipment was the contributor e.g., generator, transmission line, transformer, etc.?

? Exact location of the fault (fault locus) in the case that the fault was associated with a transmission line. This is key for determining if impedance relay settings were configured correctly for instance.

? Fault magnitude and fault clearing times. This is also key in determining if relay and breaker protection settings were configured correctly. Moreover, fault clearing times would undoubtedly affect the system’s transient stability.?

? Type of fault be it symmetrical/asymmetrical fault.

3. The root cause of the fault. This may include but not limited to:?

? Poor maintenance

? Equipment failure

? Failure due to common cause, e.g., High wind in the case of overhead lines, etc.

? Maloperation and Human error

? Substandard design?

4. Details concerning transient stability issues that were faced as it was reported from other sources that system instability resulted in several generating stations becoming islanded?

? It could be assumed that the system experienced a frequency instability event as massive amount of load was unexpectedly shed as the generators were unable recover from the rapid decay in frequency.?

? The application of or modifications to automatic underfrequency load shedding schemes could allow the grid to respond to the transient event without shedding all the load thereby creating a blackout condition.?

5. Details concerning how power was restored

? The utility was able to restore power to the nation within 12 hours or so. However, there were reports of difficulties encountered in bringing the generators online. A review of the start up procedures may be required as a minimum.

? Consideration for the use and improved maintenance of diesel generators for black start conditions need to be entertained.?

6. Discussion of any inherent design flaws and vulnerabilities and their respective correctives.?

? For instance, proper protection and coordination studies should have been done, whereby the scenario under which a blackout such as this could have been modelled and the correct protection settings could have been applied. The fact that the entire network, except the Tobago feed, was interrupted due to a fault in the south of the island of Trinidad, implies that there is a potential issue with protective device coordination. Commercially available software such as MATLAB Simulink?, ETAP?, CYME, etc., can aid in completing these analyses.?

? The network may have a topology that does not have redundancy with additional feeders and generators such that failure of one?or multiple units does not lead to a complete loss of the network

? The network does not have sufficient standby capability for regions of the grid deemed mission critical?

? Given the recent Colonial pipeline cyberattack in the US, it behooves the local power producers to conduct a detailed cybersecurity assessment to correct any potential cybersecurity issues associated with their SCADA system

? A review of asset integrity and obsolescence issues facing both the Power Generation and Transmission & Distribution institutions in Trinidad & Tobago?

7. Retrospectives

? No study of this nature would be complete without publishing key lessons learnt from the event. The positive and negative aspects of the event should be clearly documented.

Such a case study would inform and educate the public concerning this disruptive event. Proper communication of this case study to stakeholders in technical fields of engineering within the country should also be considered as such scenarios are not limited to power producers but can occur within many industrial settings such as processing plants where an unexpected blackout can negatively impact business continuity safety and can create other deleterious effects.?

This case study should be led by a team of technical experts in the field of power system engineering, who are competent in completing power systems analysis that would include but not limited to:

? Device Coordination?

? Transient Stability Studies?

? Dynamic Load Flow?

The team should be multi-disciplined as there can be several combinations of imitating causes that led to the blackout. As a minimum, persons on this team should have backgrounds in:?

? Electrical Engineering (as mentioned earlier)

? Mechanical Engineering (with experience in rotating mechanical equipment I.e., gas turbines)

? Reliability engineering?

? Mechanical/Electrical maintenance

? Project Management

Investigations, in their “traditional” sense tend to be punitive and do not really solve anything but rather create a chaotic atmosphere of blame.

To reiterate, a case study of the event should be done by an independent and competent team of technical experts who are unbiased and are not guided by political or social influences, but rather by science and recognized and generally good engineering practices.?