The information message 8.80 indicates the date and time stamp on the LIM has reverted to default factory settings. Setting the LIM clock will remove the information message. Refer to "Menu Settings" section in the Instruction Bulletin "NAE2025012" for detailed information on setting the Date and Time.
- The date and time stamp reverts to factory settings if the LIM has a loss of power for longer than 10days
NEC 517.160 (A) (5) Conductor Identification.
The isolated circuit conductors shall be identified as follows:
(1)Isolated Conductor No. 1 — Orange with at least one distinctive colored stripe other than white, green, or gray along the entire length of the conductor
(2)Isolated Conductor No. 2 — Brown with at least one distinctive colored stripe other than white, green, or gray along the entire length of the conductor
The use of XHHN or XHHN-2 wire helps meet this requirement.
Orange shall be terminated on "Neutral" Silver Receptacle Terminal
Brown shall be terminated on "Hot" Brass Receptacle Terminal
It is important to not confuse NFPA 70 definition of "Wet Locations" with the NFPA 99 definition of "Wet Procedure Locations".
NFPA-99:2012 Sections 3.3.184 & 126.96.36.199.8 define Wet Procedure Locations and the requirements for additional protection against electrical shock in these areas.
In a simplistic method, a "Wet Procedure Location" can be determined by evaluating the type of procedures, irrigation and medical equipment planned for use in the particular area.
An Isolated Power System is required in all NFPA 99:2012 defined "Wet Procedure Locations" when an interruption of power (due to a ground fault) cannot be tolerated. NEC for electrical safety recommends isolated power systems. (Should be installed when ever a power outage cannot be tolerated during a ground fault condition.)
Conductor Identification requirements for isolated (ungrounded) conductors of Isolated Power Systems are identified in NFPA 70 (NEC) in Article 517.160.
NFPA 70 (2008 - current)
Isolated Conductor No. 1 — Orange with at least one distinctive colored stripe other than white, green, or gray along the entire length of the conductor
Isolated Conductor No. 2 — Brown with at least one distinctive colored stripe other than white, green, or gray along the entire length of the conductor
NFPA 70 (2005)
Isolated Conductor No. 1 — Orange
Isolated Conductor No. 2 — Brown
BENDER recommends Annual Preventive Maintenance of all Isolated Power Panels as well as testing and recertification after any modification to the Isolated Power System.
BENDER Annual and Bi-Annual recertification services include, but are not limited to:
- Measurements of hazard current and system impedance, both resistive and capacitive
- Applied fault testing
- Line Isolation Monitor testing
- Annunciator alarm testing
- Fault location and load monitoring testing- for panels with applicable modules
- Verification of proper equipment grounding
- Recertification report with all testing data
BENDER Certification Field Testing includes, but is not limited to:
- Visual inspection of newly installed panel for proper installation and compliance with wiring requirements per NEC 517.160
- Impedance and Hazard current measurements
- Ground continuity and receptacle polarity testing
- Receptacle voltage measurements
- Testing for Proper function of Line Isolation Monitors, remote annunciators, and any accessory modules
- Onsite Training for hospital staff on the proper use and care of isolated power systems
- Certification report with all testing data
- Certification of Limited Warranty on BENDER isolated power equipment
The LIM monitors the impedance of the isolated circuit current carrying conductors (Line 1, Line 2) with respect to ground (earth) and indicates (mA) the total current that would flow through a low impedance if it were connected between either Line and ground.
The most common reasons for the LIM to be in alarm are:
- medical equipment failure and damaged extension cords
This should be evaluated via a risk assessment. There are two (2) thoughts on this subject.
- The code minimum requirement requires the use of IPS or GFCI in all “Wet Procedure Locations”.
- The recommended and industry adopted best practice is to provide Isolated Power in any patient location where patients are intended to have a direct electrical path to the heart muscle and an interruption of power cannot be tolerated.
Designers often select resistance grounding to meet code requirements. Portable equipment used in mining for example are often required to be fed from a resistance grounded source. This in addition to ground conductor monitoring and tripping immediately on ground-fault occurrence, help protect employees that are in contact with this equipment and earth.
Awareness of arc flash potential and knowing that 80-90% of faults in a plant start out as a phase-to-ground failure has meant many customers are using high resistance grounding to increase safety. Refineries, pipelines, shore-to-ship power, pulp, paper and forestry industries, steel mills and many other industrial customers have successfully used resistance grounding.
Resistance grounding, in particular, high resistance grounding has a major advantage over solidly grounding by limiting the amount of energy released during a single phase-to-ground fault. While it doesn’t reduce the PPE required for electricians it can add to employee safety and equipment reliability.
Some sites have a standard that requires them to operate medium voltage with low resistance grounding. In some cases it was a requirement to allow operation of non-sensitive ground fault protection devices. Frequently 400 A grounding resistors are used and the breaker’s standard ground-fault function is usually adequate to detect and trip during a ground fault when there is such high current available.
Yes modern ground-fault protection devices with more sensitive ground-fault pickup levels can detect high resistance faults before they reach a level that causes extensive damage. The correct CT selection can also allow detection of faults on non-linear loads that may be outside of the standard 60 Hz pickup that some ground-fault relays are tuned to.
This is a common question and since many systems are grounded by a resistor that limits current to 10 A or 5 A it seems that a small conductor should be adequate. However you must insure your choice meets the local electrical code requirements. In many cases this means a conductor no less than #8 AWG should be used for grounding.
In more advanced NGR systems the relays will provide the level of fault current, the frequency of the fault current and the phase that the fault is appearing on. If they are also equipped with downstream ground-fault protection it will direct you to the correct feeder, MCC or even load that has the fault.
While continuity of service is one major benefit of both resistance grounding and ungrounded systems that ability should not be abused. Running with a ground fault on a system indefinitely is NOT a good idea. Many sites have a timer set on their alarms. If ground-fault alarms are not cleared in a certain number of hours then the system will start to trip. Having ground-fault tripping on non-critical circuits is a recommended to lower the probability of having a phase-to-phase fault, another good safety by design improvement that could be incorporated in systems.
No single type of ground-fault detector works on every type of power system. For instance, a residual current monitor (RCM) ground-fault relay (GFR) in combination with a zero-sequence current transformer (CT) can be used on solidly grounded or resistance grounded systems, but will need very special consideration if employed on an ungrounded (floating) system. Similarly, an insulation monitoring device (IMD) can be used on an ungrounded system, but will nuisance trip or false alarm in a grounded system.
When residual current monitoring is used, residual and fault currents are signaled before the installation has to be disconnected in the event of a fault. This way, deteriorations of the insulation level are detected at an early stage and in a reliable way.
A comprehensive readiness for operation around the clock, constant competitive pressure and high cost pressure require the highest degree of electrical safety in the power supply of industrial, functional, and residential buildings. With continuous monitoring of safety-relevant circuits for fault currents, residual currents, and stray currents, incipient critical operating states are detected at an early stage. A potential risk of personal injury, fire damage, and material damage as well as EMC interferences can thus be avoided.
The operating theory behind the relay is as follows: The power wires leading to the protected load are passed through a current transformer (CT). It is important that all hot and neutral wires are fed through the CT, and that ground conductors are not. This applies to both, single and three-phase systems, and CT’s used in this fashion are sometimes referred to as zero-sequence CT’s.
Active IMD’s are like an online mega-ohmmeter. They connect between the system phase conductors and ground. A measuring signal is constantly applied to the phase conductors and will detect an insulation fault anywhere on the system from the secondary side of the supply transformer to the connected loads. If this signal finds a path to ground, it will return to the monitor. The IMDs internal circuitry processes the return signal and trips a set of indicators when the set point is exceeded. IMDs measure in Ohms (Resistance) and not in Amps (Current). A ground fault will be indicated as “insulation breakdown”.
The AMP measurement method patented for Bender is based on a special clocked measuring voltage which is controlled by a micro-controller and adapts automatically to the prevailing system conditions. Software-based evaluation enables system leakage currents causing interference on the evaluation circuit to be differentiated from the measured variable proportionate to the insulation resistance in ohms. This means that broadband interferences as they occur, for example, during converter operation, do not adversely affect the precise determination of the insulation resistance.
The AMP Plus measurement method takes interference suppression to the next level. Devices supporting this measurement method can be used universally in AC, DC and AC/DC systems, e.g. systems with varying voltages or frequencies, high system leakage capacitances or DC voltage components. This makes them ideal for use in today's state-of-the-art distribution systems, which are usually subject to this type of interference (converters, EMC).
Level 2 chargers are also known as AC chargers. They can be found as wall boxes in homes or often in public in front of shopping centers and hotels. AC voltage is at 240 V with a maximum current of 80 A and a maximum power of 19.2 kW. These are more powerful than a typical level 1 emergency charge cord. Charging times on these are usually measured in a few hours.
Level 3 chargers are also known as DC fast chargers. Their high power level allows for relatively fast top off below 30 minutes. Powerlevels are usually in the above 100 KW range and require a utility style power backing. These are relatively big, with units that can easily reach the dimension of a typical refrigerator. Modern level 3 are often equipped with Chademo (Asian standard) and CCS (Western standard) connectors/plugs
The Chademo system originated as a competitor to CCS for a fast charging DC system. While similar, there are subtle differences limiting it to models like the Nissan Leaf and Toyato Prius amongst others. While the original standard described delivering up to 125A of direct current at up to 500V into a vehicle, the upgraded Chademo 2 can utilize nowadays up to 1000VDc and 400A. All this, with the target to charge a vehicle in the shortest possible time.
The combined Charging System CCS covers EVs using Combo 1 and 2 connectors up to 350KW in a DC fast charging system. It represents one of three systems available to the public, besides Tesla and Chademo. Like the Chademo the power levels. Currently maxed out at 350KW of available power it only lags a little behind the Chademo who tops out at 400KW.
Y capacitances are present between a high voltage DC system in a vehicle and the chassis. Usually caused by filter circuits or battery capacitance, it is the goal of an EV manufacturer to keep those low, while balancing their need to produce noise reduction. Passenger vehicle Y caps are usually below 1uF, whereas busses and trucks with their larger systems can go up to 5uF.
Requirements are 100Ohm/ volt for pure DC, 500Ohm / volt for mixed AC/DC systems. For safety reasons usually the higher value of 500 is chosen. What does that mean for the operator of an EV? If an EV has let’s say a 700V battery, then the isolation between the high voltage system and the battery frame must be higher than 700V x 500 = 350000 Ohms. If that value is decreased for whatever reason, an isolation fault alarm will be triggered and the vehicle needs to be inspected.