Category: Uncategorized

Is difficult to say something like this blog’s title but evidence is just overwhelming.

During hurricane Irma our neighborhood was left in the dark for almost a week and I don’t live in a rural area, mind you. One of those days while still in the dark and out of boredom, I rode my bike along the distribution line that feeds into our subdivision. I found two places where overgrown trees were over our 13,000 Volt feeder and in one of those I decided to take a picture, the picture above.

A simple picture of trees over our feeder, then it hits me; THIS is exactly the problem!

For the 13,000 Volt conductor to the left (with the trees over it) its maintenance is not regulated by the government and for the 230,000 Volt line to the right is strictly REGULATED. There’s NO overgrowth underneath the 230,000 Volt line, notice the clear cut with nothing even close to the big line.

The North American Electric Reliability Council (NERC) has the authority to impose up to a $1,000,000 penalty if a tree comes in contact with the 230,000 Volt line. The trees coming in contact with the 13,000 Volt line have no punitive financial consequences for the utility!

Maybe a pissed-off guy starts taking pictures and posting stuff in the internet because his light are out and the loss of revenue from the customers in the dark are the worse consequences.

NERC was created to improve the reliability of the electric system to avoid the problems caused by widespread blackouts; disruptions in society cannot differentiate between outages happening by events in the bulk generation, bulk transmission or even at the distribution level.

An outage is an outage regardless what causes it, the picture above doesn’t lie.

As it was left after hurricane María, Puerto Rico’s Electric Power Authority (PREPA) bulk electric system and the limited load connected to it in the San Juan metro area is not a stable system. It blacks out frequenty and it will continue to do so in the next few months until its load footprint grows and becomes connected with other power islands within Puerto Rico.
Electric systems need to maintain a balance between generation and load, energy cannot be stored in this system. PREPA’s power system runs at 60 cycles per second or hertz (Hz). Like any other AC system, when you have more generation than load the whole system’s frequency goes over 60 Hz and under 60 Hz when you have less generation than load.
With a large combined cycle unit and some CT peakers being the sole source for a peak of a 150 MW power island, any time one of those units comes forced offline, there is no system in place to prevent the frequency decrease resulting off of this imbalance of load and generation. System frequency will keep falling to the point where it cannot recover resulting in a complete blackout. Likewise, any sudden loss-of-load event will result in an irrecoverable overspeed condition ending in a blackout too.
Most of the under-frequency load-shedding (UFLS) blocks are possibly still un-energized, critical loads are the ones in service but they were never intended to be sheddable in the first place! They used to be critical, now food for thought.
I’m sure PREPA is already taking measures to reconfigure their UFLS posture to very agressive while they remain in their current topology.

After hurricane George hit Puerto Rico, FEMA offered half the cost, a $100M grant to the island to build an underground transmission cranking path for emergencies like the one currently caused by hurricane María. One of the conditions for this investment was for PREPA to pair the funds to finish the project.
This underground 115KV line was built and is going to be the key for a near-miraculous system restoration in the metro area. It connects the Bayamón transmission center with the Palo Seco and San Juan plants to other critical load centers.

New problems are created with the blackout, people with portable generators need to fuel them and there is not enough – in my view – installed capacity to supply all the gasoline needed to keep those portable generators running. Sadly, accidents are bound to happen mishandling the fuel. Diesel generators owners will feel the same pressure. The cost for this energy is around double the current PREPA rates and this will press all these owners as well.

No power equals no water and the slew of problems this creates. Communications are also dependent on reliable power and this by itself makes all of the other efforts harder.

It is clear the return to normality depends mostly on the restoration of the electric grid, it should be given the highest priority.

The following one-line is relevant for this story:

SLLA ==== CNTC —- PALM —- FATC

After an all-weekend line reconductoring outage on one of the two parallel 115 KV lines between the SLLA and CNTC substations everything seemed to be smooth sailing that afternoon. For the duration of the outage, all the load in what constitutes a single 115 KV loop around the region as shown on the one-line above, is being fed radially from the SLLA substation through the remaining parallel line by opening the breaker of the CNTC-PALM 115 KV line at CNTC and dividing the load just as simulated in the  load flow runs. The 38 KV lines between the same substations have N.O. ACB’s in them to avoid parallel flows over their ratings.

The time comes to energize the line, the breaker at SLLA was closed and the line was energized, the open breaker at the other end at CNTC failed to operate close through SCADA multiple times. The breaker at SLLA is opened and the breaker at CNTC closes on by SCADA. When the breaker at SLLA was commanded to close, it fails to close but luckily a substation maintenance crew wrapping up their work right at the substation was called to verify the “inoperative” GCB, they found nothing wrong with it other than the closing coil isn’t getting energized whenever the breaker control handle in the control house is rotated to the close position.

Easy-peazy, the substation maintenance supervisor resolves to energize the GCB’s closing coil directly, the operator agrees on this and the breaker at SLLA did close, coincidentally the breaker on the parallel line to SLLA at CNTC trips.
The CNTC load was left radially fed by the freshly reconductored SLLA – CNTC line while the parallel line was also radially energized with no load from SLLA.
The operator still unaware of the overall picture issues a close command on the open CNTC breaker of the CNTC -SLLA line, it closes! The GCB of the reconductored parallel line at SLLA trips too!

The substation crew notices a led flag on one of the line protection relays at SLLA. After some measurements, the relay techs determine the breaker isn’t closing because the line is not synchronizing to the system.

The operators got lucky because when their phases got swapped – by pure chance – the rotation remained the same as the original system’s.

Other utilities have not been so lucky and they’ve left a couple of towns and industries with their phase rotation in the opposite direction…for days!