Addendum to Compliance Guide for High-Voltage Longwall Regulations 30 C.F.R. Parts 18 and 75 1. Section 30 CFR 18.53(b) requires
each cover of a compartment in the high-voltage motor-starter enclosure
containing high-voltage components be equipped with at least two interlock
switches arranged to automatically deenergize the high-voltage components
within that compartment when the cover is removed. My longwall has control/communication relays installed in the
same bay as high-voltage motor contactors. The common bay is divided into two compartments by a removable grounded
metal or insulated barrier that can only be removed from inside the bay. This barrier separates the high-voltage
components from the control/communication relays to comply with 30 CFR 18.53(a). Will interlocks located on the cover of the
common bay satisfy the requirements of 30 CFR 18.53(b)? Yes. However, testing and troubleshooting can only be performed on the control/communication relays when the high-voltage components in this bay are deenergized. 2. Can protective relays such as the
overcurrent, ground-fault and ground-wire monitor relays be located in the
high-voltage motor contactor compartment? No. These relays have only low-voltage inputs and outputs. In order to prevent accidental contact with a high-voltage circuit while troubleshooting low- and medium-voltage circuits; these components must be located in a control/communications compartment(s). 3. I want to use a high-voltage
contactor with electronic circuits that provide short-circuit, overload,
undervoltage and ground-fault protection and also ground-wire monitoring as an
integral part of the contactor. Is this
contactor permitted for a high-voltage longwall? Yes. A high-voltage contactor assembly with integral electronic circuits that provide short-circuit, overload, undervoltage and ground-fault protection and also ground-wire monitoring may be installed in the motor contactor compartment provided: • The contactor and associated electronic circuits are supplied by the manufacturer as one assembly. • The low- and medium-voltage components are separated from the high-voltage components by grounded metal or insulated barriers. • All settings and adjustments to the low- and medium-voltage protective circuits are accessible without entering the motor contactor compartment. • Testing and troubleshooting are only performed on the protective circuits of the contactor when the high-voltage components in this compartment are deenergized. •
The short-circuit, overload, undervoltage
and ground-fault protection, and ground-wire monitoring meet all MSHA approval
requirements. 4.
30 CFR Section 18.53(g) requires that "Control circuits for the
high-voltage motor starters must be interlocked with the disconnect
device" What is the definition of a
control circuit? The control circuit includes all the components that are used to control the operation of the high-voltage motor starters. These components include the start/stop switches and other man/machine interface (MMI) devices, the programmable controller, if it is used to control the high-voltage starters, and protective relays for high-voltage motors. In general, the control circuit includes all components located in the control/communications compartment. 5. Low-voltage lighting circuits and
low- and medium-voltage PTO circuits are neither high-voltage motor starter
circuits nor control/communications circuits. In which compartment should these circuits be located? Although the rule does not
specifically address these circuits, the intent of the rule is to separate
circuits and components by voltage classification. When complete separation of voltage classifications is not
possible with barriers or partitions where both medium- and high-voltage circuits
or both low- and high-voltage circuits are connected to a component or device,
that component is required to be located in the motor contactor or disconnect
device compartment. If these circuits are
connected to the line side of the disconnect device, these circuits must be
located in the disconnect device compartment. The low- and medium-voltage circuits must be separated from the
high-voltage components by grounded metal or insulating board. If these circuits are connected to the load
side of the disconnect device, then they cannot be located in the disconnect
device compartment. 6. Can insulated high-voltage wiring
pass through the control/communication compartment? Yes, but the wiring must be separated from the control/communication circuits by a grounded metal or insulated barrier. 7. Can a reinforced flame-resistant
cable guard be used as the insulated barrier described in item 6? Yes. 8. Does the barrier described in item
6 require interlock switches? The barrier described in
item 6 would require interlock switches only if the barrier can be easily
removed without the removal of additional components or wiring. 9. Can low- and medium-voltage wiring
be run through the high-voltage motor starter compartment? Yes, provided the low- and
medium-voltage wiring is installed such that the low- and medium-voltage wiring
cannot contact any high-voltage components or wiring. The method of separating these classes of wiring must be
documented on the approval drawings. 10. Can the main disconnecting device
required by 30 CFR 75.815(a) be installed in its own separate enclosure? No, unless the disconnect enclosure is physically attached to the power center to become an integral part of the power center. The physical connection must be rigid and substantial. 11. My longwall shield pumps are not included
in my Part 18 longwall approval. Are
these pumps considered longwall equipment that must be deenergized by the main
disconnecting device required by 30 CFR 75.815(a)? Yes. The Part 18 longwall approval only specifies equipment that is required to be permissible. When the longwall shield pumps are not located within 150 feet of longwall faces, they are not required to be permissible and therefore the pumps are not required to be listed on the Part 18 longwall approval. The disconnecting device that is required by 30 CFR 75.815(a) must deenergize all longwall equipment that are moved as the longwall face retreats, including equipment that may not be listed on the Part 18 longwall approval. Stationary longwall shield pumps and other stationary equipment that are located at the mouth of the longwall section are not required to be deenergized by the main disconnecting device. 12.
My longwall uses a combination power
center/high-voltage motor starter assembly. The only high-voltage cables extending from this assembly are the cables
extending to the high-voltage motors or the shearer. These cables are each provided with instantaneous ground-fault protection as required by 30 CFR
75.814(a)(5). Are these cables high-voltage circuits extending from
the section power center that must be provided
with ground-fault protection described in 30 CFR 75.814(a)(4)? The cables extending from this assembly are high-voltage cables extending from the section power center and must be provided with ground-fault protection per 30 CFR 75.814(a)(4). One device may be used to provide the protection required by 30 CFR 75.814(a)(4)(i) and the protection required by 30 CFR 75.814(a)(5) for these cables. The mining industry has, in the past, provided separate devices to meet these requirements and MSHA encourages this design. In addition, the system must have two separate devices, one to comply with 30 CFR 75.814(a)(4)(ii) and the other to comply with 30 CFR 75.814(a)(4)(iii). 13.
Section 30 CFR 75.814(a)(4)(iii) requires thermal
protection for the grounding resistor be set at 50 percent of the maximum
temperature rise of the neutral grounding resistor. How is the maximum temperature rise of the neutral grounding
resistor determined? The maximum temperature rise of the neutral grounding resistor is the increase in resistor temperature with the maximum system ground-fault current flowing through the resistor. The thermal protection must be set at 50 percent of this value. 14.
Do the new regulations require any tests or
inspections of the equipment before being placed in service? All longwall
systems must be approved as permissible under 30 CFR Part 18. New designs submitted for approval will
require a field inspection of the system by the MSHA Approval and Certification
Center prior to being placed in service. Longwall systems built or rebuilt according to an existing approval do
not need an inspection by the MSHA Approval and Certification Center. However, MSHA enforcement personnel will
inspect the equipment for compliance with the regulations and may be available
to provide
compliance assistance and inspect or test longwall equipment at
locations away from the mine. |