EXHIBIT 44 

Case:17-03283-LTS Doc#:4014-40 Filed:10/04/18 Entered:10/04/18 16:51:23 Desc:

Exhibit 44 Page 1 of 3
Recent Circuit Breaker Fire & 

Status of Circuit Breakers in the Puerto Rico Electric Power System

At approximately 9:00 PM on the evening of Sunday, February 11, 2018, a violent explosion occurred at

the Monacillos Transmission Center (“MTC”) when a 115 thousand-volt (“kV”) Oil Circuit Breaker (“OCB”) 

ruptured. The MTC is located southeast of the city of San Juan (see Figure 1). The OCB that exploded was 

a General Electric unit that was installed in 1975, with over forty years of service. It was extremely 

fortunate that the explosion occurred at a time when no personnel were present, and there were no 

resulting injuries. 

Figure 1: Map of San Juan area 115 kV lines with Monacillos shown

The ruptured OCB is being replaced by a SF6 (sulfur hexafluoride) breaker at a cost of approximately 

$100,000, with an estimated repair time of eight days. A SF6 breaker represents a newer technology than 

the OCB technology.

Upon investigation and review of the existing records of OCBs on the PREPA system, it was discovered 

that there are 28-230 kV breakers and 134-115 kV breakers that are similar to that which ruptured at 

Monacillos. In addition, there are also 267-38 kV OCBs, plus 259 OCBs of lower voltages. While OCBs have 

been successfully used in the utility and industrial arena for years, in the case of PREPA, the age of some 

of these units causes a level of concern.

Circuit breakers, as the name implies, break a circuitto protect that circuit when an overload (high current) 

or short circuit (very high current) occurs. At lower voltages, a circuit breaker can simply open a set of 

contacts (at high speed) in air, and any arc between the contacts will be extinguished. However, as 

voltages increase, the speed and distance between contacts needed to extinguish an arc becomes too 

great from a practical standpoint, so different mediums are used between contacts that provide for arc 

control. One of the mediums that was used early on was oil. The oil used in OCBs is the same type that is 

Confidential Information PREPA-AHBHG0012808

confidential

Corey Brady

Weil Gotshal

Feb 15, 2018 01:42

confidential

Corey Brady

Weil Gotshal

Feb 15, 2018 01:42

Case:17-03283-LTS Doc#:4014-40 Filed:10/04/18 Entered:10/04/18 16:51:23 Desc:

Exhibit 44 Page 2 of 3
used in transformers, and because of its properties, this oil insulates not only the contacts but also the 

high voltage components in the breaker from the container that the components are immersed in. 

While OCBs are reliable and low-cost units, the dielectric strength (the ability to prevent arcing and 

electrical conduction) of the oil tends to weaken over time due to age, contamination by gases, and 

introduction of carbon particles which are produced when the breaker operates. Another consideration 

with OCBs is that the oil is flammable, and when dielectric strength becomes too weak, an explosion like 

the Monacillos event can occur. 

Figure 2: Breaker Post Explosion Figure 3: Resulting Fire post OCB Explosion at Monacillos

As can be seen from the pictures above, internal failure of an OCB can be catastrophic and dangerous not 

only to life and limb of personnel that might be in the area, but also to buildings and structures in proximity 

to the breaker failure.

It cannot be over-emphasized how important properly operating circuit breakers are to an electric system. 

There are OCBs that have been in operation since 1969 on the PREPA 230 kV system. The 115 kV system 

has OCBs that have been in operation since 1949, as does the 38 kV system. We are undertaking a review 

of the breaker system to determine the proper course of action for replacement in the future.

Confidential Information PREPA-AHBHG0012809

confidential

Corey Brady

Weil Gotshal

Feb 15, 2018 01:42

confidential

Corey Brady

Weil Gotshal

Feb 15, 2018 01:42

Case:17-03283-LTS Doc#:4014-40 Filed:10/04/18 Entered:10/04/18 16:51:23 Desc:

Exhibit 44 Page 3 of 3