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The Power inThe Power in

Electrical SafetyElectrical Safety

Bender Group

Robbie Mewton 11-9-2019

2BENDER Image Presentation

Agenda and Contents

Contacts:

Robbie Mewton Applications Engineer – Mining/Oil & Gas [email protected]


Agenda

General Electrical System Earthing LayoutsGeneral Electrical System Earthing Layouts

Bender Monitoring EquipmentBender Monitoring Equipment

International and Local RegulationsInternational and Local Regulations

DiscussionsDiscussions

IntroductionIntroduction


A big idea, which still drives us to this day.

A big idea, which still drives us to this day.

Walther Bender‘s vision over 70

years ago: comprehensive

protection against the dangers of

electrical current in the mines of

Germany


Global Player

Family enterprise actively

managed in third

generation

700 employees on 4

continents, 15 %

employed in research

and development

€110 Million Euro

turnover

14 International subsidiaries

70 International representations

Bender Benelux

Bender Canada

Bender China

Bender Germany

Bender Iberia

Bender India

Bender Ireland

Bender Italy

Bender Latin America

Bender Russia

Bender Switzerland

Bender Thailand

Bender USA

Bender UK

Low Mill Business Park Ulverston – Cumbria – LA12 9EE

6BENDER > Image Presentation

Innovative Solutions

that identify risksbefore they occur.

Innovative Solutions

that identify risksbefore they occur.

We develop solutions for the electrical safety in a great variety of complex

applications.

Our trendsetting products protect men and machines and avoid downtimes.

Bender PhilosophyBender Philosophy


Solutions by Bender –for a high variety of applications

Energy and Utilities Rail and Metro Critical Infrastructure Healthcare

Manufacturing Oil, Gas, Mining eMobility Harbors and Vessels


Agenda







Depending on the purpose and the application many

solutions are available on the market

Electrical System Earthing Design

Over 90% of all Electrical faults are Earth faults


System Earthing Design Criteria

Höherer ErdungswiderstandHöhere UnfallsicherheitHöhere Brandsicherheit

Optimierte InstandhaltungHöhere BetriebssicherheitHöhere Wirtschaftlichkeit

Permissible earthing resistance

Accident prevention measuresProtection against fire

Optimized maintenance

Operational safetyEconomic efficiency

11BENDER Image Presentation 11

The neutral conductor is connected to the equipotential

bonding (earth).

No live conductor of the system has a conductive, low-

resistance connection to the equipotential bonding

system (earth).

The essential difference between IT and TN systems

IT System TN System


Operational safety

In the event of an insulation fault RF no more than a small

capacitive current flows ICe

The fuse will not be triggered

The voltage supply is maintained in the event of a

single-pole earth fault

No unexpected operational interruptions

Indication ISOMETER® (<R)

Insulation fault

An earth fault current flows dependent on the value of

the insulation resistance.

IF < IK The fuse will not be triggered -

Danger of Malfunction

No indication

IF > IK The fuse will be triggered -

Unexpected operational interruptions

Considerable consequential costs

... in the TN system

Insulation fault … in the IT system


Personal safety accident prevention measures – touch voltage limitation

On the occurrence of a fault, a very low current ICe depending on the

system leakage capacitance Ce flows.

In case of PE conductor interruption, this current

can flow via the body.

In small and medium-sized installations ICe is very low and also the

highest possible touch current IB.

Persons are not injured if direct contact occurs between conductor

and earth.

In the event of a fault, high fault currents IF occur,

which may flow via the body in case of PE conductor interruption.

Immediate disconnection is required.

The touch current IB is essentially determined by the body

impedance.

Use RCD/ground fault protection

Insulation fault ... in the TN system



Protection against fire

A small current will flow limited by

the high impedance of the fault loop

Substantially reduced fire risk

Increased protection for

personal and equipment

If the fault current IF …

IF < IK The fuse will not be triggered -

Danger of Malfunction

No indication

IF > IK The fuse will be triggered -

Unexpected operational interruptions

Considerable consequential costs

Insulation fault ... in the TN system



Permissible earthing resistance

In IT systems a higher earthing resistance

is permissible: UB = RA x Id

RA = earthing resistance

Id = fault current

UB = permissible touch voltage

≤ 50 V according

to IEC 60364-4-41

and IET Wiring Reulations,18th Edition

Frequently used in applications

where it is difficult to realize a low earthing

resistance e.g. mobile generators


Resistance grounded system

NG

R

XC0

3IC0

GroundFault

IG

3IC0IR

IR

� ��

3��

Low resistance grounded

Ground-fault current limit between 100A and

1000A

Availability behaviour similar to solidly grounded

system

High resistance grounded

Ground-fault current limit between 5-25A,

normally less than 10A as per IEEE std. 142-

2007

Mainly for plant protection in LV&MV, popular in

Americas, no trip on first fault, locate and rectify

Availability behaviour is a compromise between IT

and solidly grounded for machine availability Do not use line to neutral loads ...

industrial applications


Resistance grounded system


different grounding systems – solidly grounded

High currents in case of

ground fault.Solid tripping.

High energy at point of fault (arcing, fire

hazard).

Fixed potential at

neutral.

No voltage shift under ground fault condition.

Line-to-Earth overvoltages will

directly affect load circuits.

Relay coordination

Faulty circuit will be highlighted/switched off at relatively Lo-

Ohm value

High currents require ground fault

protection at main breaker.

Monitoring


different grounding systems – ungrounded

Low currents in case of

ground fault (3*IC0).

No tripping (system still

running).

No inherent indication of

fault.

Neutral not existent or

floating.

Voltage Shift at healthy phases

(VLG=>VLL).

Ground Fault Indication

Real insulation value and Hi–

Ohm fault location

Monitoring


different grounding systems – resistance grounded

Limited current in case of

ground fault.

Low energy at fault location.

Neutral grounded

through NGR.

Advantages of ungrounded and solidly grounded.

Voltage Shift at healthy phases

(VLG=>VLL).

NGR Monitoring

Evaluate resistor,

connection and fault current.

Not immune to harmonics and

unbalance.Monitoring


Agenda







Our Philosophy –Pre-Warning and continuous monitoring

RCD

RCMS

Operation

Operation

Interruption

RepairPlan ServiceInfoOperation

Plan Service

Service

Repair

Disconnection

Alarm


Insulation fault location as per IEC61557-9 – IT System

IL

Comms/Sensor Bus

ALARM

Insulation fault

! 5 mA

BS Bus 2 Chan 3

2/2

ALARMALARM

Insulation fault

! 5 mA

3rd Motor

2/2

ALARM


Residual current monitoring for TN system – BS EN 62020/ BS EN 50628:2016

Sensitive monitoring e.g. from 1mA for

developing insulation faults

Pre-warn against electric shock and

potential fire hazard

AC + DC sensitive

Continuous monitoring of cables and

connected loads

No requirement to disconnect for

periodic Insulation resistance testing

Comms


HRG Monitoring and fault location

Motor Motor

CD

NG

R

BCOM

BMS

e.g.:

��


DC residual currents impact on the installation with Type A or AC RCD

Background - Type A RCD is influenced by DC residual

currents:

Type A RCD is designed for 50Hz a.c. fault currents

and only allows DC residual currents up to 6mA.

For fault currents ≥ 30mA, the Type A RCD must trigger after

40ms to prevent ventricular fibrillation.

A DC residual current "brings" the core used in the RCD to

saturation

Shift of the core characteristics

At low excitation current.

→ Type A RCD no longer triggers according to the

specification

+IDC

If (a.c.)

Itrip (a.c.)

If (a.c.)

Itrip (a.c.)


RCD limitations – VSDs/Inverters/SMPS

Type B RCD >6mA DC component


PE/Loop conductor monitoring and pilot wire monitoring

GM420

PE Loop monitoring

RC48C – RCM plus PE-PW monitoring for resistance, open and short

For trailing/mobile equipment cable protection

For fixed PE/earthing connection monitoring


Bender proven solutions typical areas

Ventilation of underground mines is a crucial criterion for their operational

safety. An interruption to the ventilation is potentially life-threatening for the

miners, includes an increased fire risk and failure of the production system. This

means continuous residual current monitoring using RCMS is vital, as it detects

any hazardous changes to the power supply immediately.

Ventilation A reliable supply of air


Bender proven solutions typical areas

Drainage of underground mines is incredibly important. Any interruption to the drainage

system increases the risks of shafts filling up with water and people being put in danger.

From this perspective, continuous monitoring with ISOMETER®s or RCMS residual

current monitoring systems is essential. They immediately recognise hazardous changes

in the power supply.

Drainage Water - a life-threatening risk underground

Main Control RoomThe ability to monitor report and act is crucial and Benders Powerscout platform gives

full visibility across all installed systems and products to give a mine complete sitewide

electrical overview.


Agenda







International Standards & Regulations

AS/NZS 2081:2011: Electrical

protection devices for mines

and quarries

Australian general practice has always favored the solid earthing of the neutral (TN), or its

equivalent, at multiple points on a system (MEN) to assist in the control of touch and step

potentials and ensure the reliable operation of electrical protection devices. Mining practice

has been to use a high impedance star-point to earth connection system (IT) […] By limiting the magnitude

of earth fault currents, high step or touch potentials do not occur and stray currents do not affect the safe

functionality of other electrical systems.

NER (where used) – monitoring required

Earth continuity monitoring required

CSA: Canadian Electrical Code

/ CSA C22.1-15

Section 10 – Grounding and bonding

Where line to neutral loads are served continuous NGR monitoring required.

CAN/CSA M421-00 Section

3.5.5

Where ground-fault protection is used, the supply shall be:

• Grounded through a neutral-grounding device that limits ground-fault voltage to 100V or less

CAN/CSA M421-00 Section

3.6.2

General –Grounding –Neutral-Grounding Devices

• Continuous monitoring is required on any NGR

• De-energize supply in less than 60 s if NGR opens

IEEE 142:2007 Grounding of

Industrial and Commercial

Power Systems

1.2.7 high-resistance grounded:

A resistance-grounded system designed to limit ground fault current to a value that can be allowed to flow for an

extended period of time, while still meeting the criteria of R0<Xco, so that transient voltages from arcing ground

faults are reduced. The ground-fault current is usually limited to less than 10A, resulting in limited damage even

during prolonged faults.

1.2.8 low-resistance grounded:

A resistance-grounded system that permits a higher ground-fault current to flow to obtain sufficient current for

selective relay operation. Usually meets the criteria of R0/X0 less than or equal to 2. Ground-fault current is

typically between 100A and 1000A.



IEC 60364-1, Section 131 Per 250.36 High-Impedance Grounded Neutral Systems, high-impedance grounded neutral systems in which a

grounding impedance, usually a resistor, limits the ground-fault current to a low value shall be permitted for 3-

phase ac systems of 480 volts to 1000 volts where all the following conditions are met:

1. The conditions of maintenance and supervision ensure that only qualified persons service the installation.

2. Continuity of power is required

3. Ground detectors are installed on the system

4. Line-to-neutral loads are not served.

IEC 61892-2; Section:

5.4 Neutral earthing for

systems up to and including

1000V

5.5 Neutral earthing for

systems above 1000V

5.4.1 The neutral point shall either be directly connected to earth or through an impedance.

5.5.1 Earthed neutral systems shall limit the earth fault current to an acceptable level either

by inserting an impedance in the neutral connection to earth or by an earthing transformer. Direct earthing

shall not be used for these systems.

NORSOK (Norwegian

Standard) E-001

5.2.2 Neutral earthing for system up to and including 1000 V (see IEC 61892-2)

The neutral shall be earthed through a resistance with numerical value equal to or somewhat less than 1/3 of the

capacitive reactance between phase and earth.

5.2.3 Neutral earthing for system above 1000 V (see IEC 61892-2)

The system earthing methods for the different voltage levels […]. For high voltage levels (>1000V), the system

earthing shall be performed as “High resistance earthed neutral”.

The neutral shall be earthed through a resistance with numerical value equal to or somewhat less than 1/3 of the

capacitive reactance between phase and earth.



MSHA (Regional US requirements) MSHA expressed a concern with limiting the amount of energy dissipated in an

explosion-proof enclosure during a ground fault. Title 30, Code of Federal Regulations,

requires that maximum ground fault current be limited to 25 A for low- and medium-

voltage circuits. However, the industry adopted a more conservative 15 A limit.

Pennsylvania Bureau of Mine Safety Mine Power Substation

• Ground fault-current limiting resistor protection

Load Center

• Ground fault by potential protector in the event of an open ground resistor

• Continuous monitoring of the ground resistor is acceptable in lieu of potential

protector

Mining Canada In Mining in Canada it is clearer:

•Any where ground-fault protection is used high-resistance grounding is required.

•Any where high-resistance grounding is used the NGR must be continuously

monitored.

So far there are no official regulations requiring protection at low

frequencies and DC but MSHA has been recommending that users install

low-frequency ground-fault protection.

Canada has not yet addressed the problem, while Australian

authorities are keenly aware of it.


NFPA

• USA

NFPA NEC 2005 Art 250.188 (D)

Ground-Fault Detection and

Relaying.

Require to

Monitor PE/ earth conductor for mobile miningequipment and ensure tripping of ground faultprotection is effective.

80 años de experiencia

Canadian

CAN/CSA-M421-00 (R2007): Use of

Electricity in Mines (Uso de

electricidad en Minas).

Peru

Health and Safety executive 024-

2016


Agenda







UK Mining Regulations

• HSG 278 (HSE)

• Confusion over the use of IT system – need clarification see clauses 80-83

• BSEN 50628:2016

• What will be the significance of this standard

• Has few differences from HSG278

• Allows the use of IT system

• Recommends use of RCM AC/DC sensitive



Open Discussions

• Some topics from Bender UK

• Use of AC/DC sensitive RCD/MRCD in ground fault protection due to the use inverter drives, inline

with BS7671:2018

• Is/will IT systems be allowed in the UK mines with monitoring

• PE/Pilot conductor monitoring

• NGR active monitoring for O/C, S/C and resistance/deenergised status

• How can Bender help to make UK mining safer and cost effective e,g standards, education etc etc



Bender GmbH & Co. KG

www.bender.de

Pictures: Bender archive, www.pixelio.de, www.fotolia.de, www.istockphoto.com, Fraport AG

Subject to modification - © Bender GmbH & Co. KG, Germany

The presentation, its content, pictures and drawings are protected by copyright law. Duplication, translation, microfilming and transfer into any electronic systems, especially for commercial purposes is not allowed and subject to approval by the issuer. We do not assume any responsibility and liability for faulty or missing content. All data is based on manufacturers‘ information. All logos and product descriptions are registered trademarks of the respective manufacturer.

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