I-Gard SENTINEL Manuel utilisateur

C-107EM Instruction Manual, January 2015

HIGH RESISTANCE GROUNDING

SENTINEL

I-Gard’s commitment to electrical safety provides both industrial and commercial

customers with the products needed to protect their electrical equipment and the

people that operate them.

As the only electrical-safety focused company whose product portfolio includes

neutral grounding resistors, high-resistance grounding systems and optical arc

mitigation, we take pride in our technologies that reduce the frequency and

impact of electrical hazards, such as arc ﬂash and ground faults.

For those customers who have purchased from us over the last 30 years, you

know us for the quality and robustness of our products, our focus on customer

service and technical leadership. We build on this foundation by investing

in developing new products in electrical safety education - including EFC

scholarship program - by actively participating in the IEEE community programs

on technical and electrical safety standard, and working with local universities

at discovering new technologies. We remain unrelenting in our goal of improving

electrical safety in the workplace.

Our commitment to excellence is validated by long-standing relationships with

industry leaders in ﬁelds as diverse as petroleum and gas, hospitals, automotive,

data centers, food processing, aerospace, water and waste water plants, and

telecommunications. We provide our customers with the product and application

support required to ensure that their electrical distribution system is safe and reliable.

ABOUT I-GARD

SUBJECT PAGE

1. General Description ..................................................................................................................4

2. High-Resistance Grounding ....................................................................................................5

3. Installation .................................................................................................................................6

4. DSP Connecting Instructions ..................................................................................................8

5. Operation/Set-Up ....................................................................................................................11

6. Additional Information .............................................................................................................11

FIGURES

Figure 1: Interior View ..................................................................................................................6

Figure 2: Sentinel Schematic Delta Connection ........................................................................6

Figure 3: Mounting Holes Dimensional Details ..........................................................................7

Figure 4: Knock-Out Locations ...................................................................................................8

Figure 5: Preferred Feeder Module DSP-DFM Wiring ...............................................................9

Figure 6: Alternative Sensor Wiring ...........................................................................................10

Figure 7: Typical 4-Wire Communications Connection ...........................................................10

TABLE OF CONTENTS

1. GENERAL DESCRIPTION

I-Gard Sentinel is designed to detect and alarm the occurrence of a ground fault, to identify the faulted feeder and

to provide selective second ground fault tripping. In addition to other operational and safety features, the Sentinel,

through the pulsing feature, allows maintenance personnel to locate the fault and to isolate it promptly. The Sentinel

system can assist in locating the fault with pulsing circuitry. In the event of a second ground fault, the Sentinel acts

quickly to prevent the loss of two feeders by selectively tripping the lower priority feeder only.

MODBUS communications allows the operator to remotely monitor which feeder is faulted and to monitor the leakage

currents of all feeders for trending purposes. The cyclic pulsing combined with the hand held current sensor, and a

single line diagram can be used to rapidly locate a ground fault even in complex power distribution systems.

The Sentinel system includes a DSP-OHMNI system consisting of digital display mounted at the front panel

and a number of modules mounted inside the Sentinel enclosure. The modules are connected together through

20-conductor standard ribbon cable. A panel-mounted display module provides a human interface to the system

and communications on RS-485 common port which allows set-up and control. There are ﬁve DSP-OHMNI modules

as follows:

• DSP-DM Display Module

• DSP-DPS Power Supply

• DSP-DSM System Module

• DSP-DFM Feeder Module

• DSP-DRM Resistor Monitor

DSP System can be expanded to 50 feeders for large installations, each branch with a dedicated feeder module

and sensitive zero-sequence current sensor. The digital display indicates the faulted phase, the total system leakage

current in percent of the let through current of the OHMNI-PM and provides other information such as priority

settings and the neutral grounding resistor setting. It is used to program the system and to provide manual control

of the pulsing function.

The feeder modules measure the fault current level in the branch circuits that are protected. These modules use

standard I-Gard zero sequence current sensors Type T2A, T3A, T6A and T9A (sold separately). Each feeder module

is equipped with a form C contact, 10A relay that is normally used for tripping the protective breaker. The DSP-DFM

detects two fault levels. Firstly it detects the single fault, which creates a system alarm condition, and secondly

through a priority level system it provides breaker control to disconnect the least important circuit breaker.

Communication is provided by a 2-wire or a 4-wire RS-485 network from a jack located at the rear of the DSP-

DM Display Module connected to the terminal block for easy customer connection. The communications protocol

supported is MODBUS RTU, which is a master/slave system with selectable baud rates from 4800 to 19200. The

DSP supports the MODBUS function read holding registers only, without exception support. Additionally it will

support remote RESET using the force coil function.

The DSP system is used in conjunction with a voltage sensing unit type DDR2. The DDR2 matches the DSP-DSM

input circuits to the system voltage. The most common types are the following:

DDR2-1 120 V*

DDR2-2 240 V

DDR2-4 480 V

DDR2-6 600 V

TYPE SYSTEM VOLTAGE

*Also used with potential transformers for higher voltage systems.

The DDR2 provides output voltages VAG, VBG, VCG that are proportional to the phase to ground voltage and also

voltage VNG that is proportional to voltage across the neutral resistor (i.e. Total leakage/fault current of the system).

The current-limiting resistance is connected between the ground and the neutral point of the transformer on Wye

systems. On delta systems an artiﬁcial neutral device (I-Gard Type DDAI) is required to provide a neutral point.

The DDAI device is selected for appropriate ‘let-through’ current, i.e.: the current, which will ﬂow to ground, if there

is a short circuit from line to ground.

DDAI device is available for continuous currents of 1 ampere to 10 amperes for system voltages listed above.

For further information regarding the use of this device refer to:

Instruction Manual Type DDAI Artiﬁcial Neutrals

C-430EM.

2. HIGH-RESISTANCE GROUNDING

Some electrical codes allow continuous operation of the electrical system with one phase faulted to ground

provided that certain limitations on the system voltage and ground fault current are met, including a requirement to

locate and isolate the ground fault as fast as possible.

In a similar fashion, the Canadian Electrical Code, Part 1, C22.1 and the National Electrical Code, NFPA 7, allow the

use of high-impedance grounding neutral systems up to 1000VAC where the ground fault current is limited to 5A or

less. These new changes to the electrical code allow users of the I-Gard Sentinel to maintain a ground fault current

of 5A or less on their electrical distribution system without interruptions caused by a single ground fault, thereby

avoiding unscheduled shutdowns and production interruptions. I-Gard Sentinel users can locate, isolate and repair

faulty equipment at convenient time.

The reason for limiting ground fault current by resistance grounding may be one or more of the following, as

indicated in IEEE Std. 142-1991, IEEE Recommended Practice for Grounding of Industrial and Commercial Power

Systems. pp. 25-26:

1) To reduce burning and melting effects in faulted electric equipment, such as switch gear, transformers, cables,

and rotating machines.

2) To reduce mechanical stresses in circuits and apparatus carrying fault currents.

3) To reduce electric-shock hazards to personnel caused by stray ground-fault currents in the ground return path.

4) To reduce arc blast or ﬂash hazard to personnel who may have accidentally caused or who happen to be in

close proximity to the ground fault.

5) To reduce the momentary line-voltage dip occasioned by the occurrence and clearing of a ground fault.

6) To secure control of transient over voltages while at the same time avoiding the shutdown of a faulty circuit on

the occurrence of the ﬁrst ground fault.

Figure 1: Interior View

3. INSTALLATION

I-Gard Sentinel is housed in a NEMA 3R (IP-33) indoor rated enclosure containing the neutral grounding resistor,

ground fault relay and isolation switch. Upon receipt, carefully open the protective shipping carton, remove all

packing material and visually inspect the assembly. If the unit is damaged, immediately process a claim with the

freight company. Do not proceed with installation. Contact I-Gard Corporation at the numbers listed on the ﬁnal

page of this document.

Turn the Isolation Switch to OFF position and loosen the two door bolts to open the front door to access the

mounting holes.

Figure 2: Sentinel Schematic Delta Connection

Figure 3: Mounting Holes Dimensional Details

The wall mounting holes are located in the rear corners of the cabinet (Figure 3). Since there are two enclosure sizes

depending on the number of feeders included in the I-Gard Sentinel, the distance between mounting holes are

indicated in the table below.

30” x 30” Up to 10 26 ¾” (679.5mm) 26 ½” (673 mm)

36” x 30” Up to 15 26 ¾” (678.5mm) 32 ½” (825.5 mm)

ENCLOSURE DIMENSION NUMBER OF FEEDER

MODULES

DISTANCE BETWEEN MOUNTING HOLES

VERTICAL HORIZONTAL

Mounting holes are 3/8” or 9.5 mm wide allowing the use of 5/16” or 9 mm diameter fasteners.

Mount the I-Gard Sentinel securely to the wall in accordance with local codes. Once the I-Gard Sentinel is securely

mounted, proceed to the connections. Electrical access to the interior is provided by means of eight knock out

openings (See Figure 4) suitable for ½” or 13 mm conduit. Two are located near the bottom of each side and two are

located in the bottom near each sidewall. I-Gard Sentinel 3-phase system is available in a variety of voltages that

connects to the appropriately labeled terminal blocks (See Figure 5). Connect phase A to terminal block marked A,

phase B to terminal block marked B and phase C to terminal block C. The supply cable size should be no smaller

than size 14 AWG or size 2.5 in metric system, in agreement with local electrical authority code. Connect the system

neutral to the point identiﬁed as N on terminal block and the system ground to the point identiﬁed as G. Both the

Canadian Electrical Code and the National Electrical Code require a minimum size 8 AWG or size 10 in metric

system if conduit is used and size 6 AWG or size 16 in metric system if the neutral to ground wire is exposed.

IMPORTANT NOTE: System neutral (N) must be connected to a single point only. All conductors must be insulated

to the full system voltage.

Figure 4: Knock-Out Locations

4. DSP CONNECTING INSTRUCTIONS

All the wiring is between sensors and modules is 14 AWG or 2.5 size in metric system switchboard wire, which need

not be shielded. 4-wire shielded cable should be used for the serial communications. A typical wiring schematic is

shown in Figure 5.

Sensor wiring is not generally limited by length and may be up to a kilometer without degradation of performance,

since the sensor is a current source. Sensor wiring should be run in separate conduit from Power wiring. The

recommended sensor wiring connections are shown in Figure 5. Two wires should be run from each sensor X1

and X2 as indicated to prevent cross coupling between Modules. If existing wiring does not allow this connection

because of common connection at X2 as has been common in some installations, then the G terminals of the DSP-

DFM modules should be connected as shown in Figure 6.

The wires from the zero sequence current sensors to the feeder modules should be twisted.

The RS-485 cable shield should be grounded at the ground terminal provided on the 5-pin jack as shown in Figure

6, which shows a typical installation with a local computer and LAN.

Communications may be supported as a node in an existing MODBUS network or may be connected through a

standard RS-485 to RS-232 converter to a PC with supporting software.

The alarm contacts numbered 5, 6 NO and 5, 9 NC, are available at the DSP-DPS as a Form C type and should be

connected to operate a horn or other means to alert an operator to the fact that a fault has occurred on the HRG

system. The contacts are rated at 10A, 240V AC Resistive. The contacts are located on the terminal blocks at the

bottom of the enclosure.

Always perform a ﬁnal inspection. All foreign objects must be removed from inside the enclosure. All conductors

must be secured in the proper positions before closing the door and energizing the system.

DO NOT ENERGIZE the I-Gard Sentinel unless the door is closed and secured by the two bolts provided.

DANGER

Hazard of Electrical Shock, Burn or Explosion

All installation, servicing and testing referred to in this manual must be

performed by qualiﬁed personnel. All power should be disconnected

prior to removing covers or enclosures and where live conductors

may otherwise be exposed.

Failure to observe these precautions may result in death or severe

personal injury and damage to equipment. Before placing an

intentional ground fault on the power system, check that a fault does

not already exist. Any test ground fault equipment must be rated for

full system voltage and be fused for protection.

Figure 5: Preferred Feeder Module DSP-DFM Wiring

Figure 6: Alternative Sensor Wiring

Figure 7: Typical 4-wire Communications Connection

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