////// SUBSTATIONS

Voltage Limiting Device

VGuard

Voltage limiting DeVice / Vguard2

GENERAL INFORMATION

in order to limit these voltages below the admissible values defined in en 50122‑1 standard, a voltage limiting device must be used as a short‑circuiter between negative and earth.

During normal operation of railway system, dangerous voltage can occur across accessible points of the return circuit and earth due to the voltage drops along the return circuit caused by the current train traffic or insulation fault.

VOLTAGE HAZARD

RUNNINGRAIL

EARTH

VGuard

MAIN BENEFITSMAIN BENEFITS D Fast response time.

D combined protection of personnel, passengers and installation.

D Prevention and elimination of dangerous voltage.

D low residual voltage guaranteed.

D automatically recoverable.

D Bidirectional operation and protection.

D continuous monitoring of the potential of the return circuit.

D manually operable on site.

D movable connections allowing to by‑pass and isolate the equipment in safe way during test or maintenance task on the system.

STANDARDS

Sécheron’s voltage limiting devices (Vguard) are recoverable devices which are compliant with the railway standards:

• for voltage limiting device of classes 3 and 4, according to en 50526‑2 standard.

• for protective provision about electrical safety in VlD‑F, VlD‑o or both functions, according to en 50122‑1 standard.

Voltage limiting DeVice / Vguard 3

VARIANTS

TECHNICAL DATA

Sécheron is able to supply two main variants of Vguard:

Both variants are available for indoor (iP42) or outdoor (iP65) application. IP65 variantIP42 variant

/// VGuard-B

Basic Vguard with contactor.

class 3 according to en 50526‑2 standard.

/// VGuard-H

Hybrid Vguard with contactor and thyristors.

class 4 according to en 50526‑2 standard.

VGuard-B VGuard-H

VGuard-B-50 VGuard-B-100 VGuard-H-50 VGuard-H-100

Configuration

Rated voltage [Un] 900 to 3600 VDc 900 to 3600 VDc

Rated current [iR] 1000 a 1200 a 1000 a 1200 a

instantaneous triggering voltage [Uti]

n/a 300 or 600 V

tolerance on instantaneous triggering voltage

n/a300 V: 10%600 V: 5%

instantaneous response time [tRi] n/a < 5 ms

nominal triggering voltage [Utn] 50 to 750 V 50 to 750 V

Response time [tR] < 100 ms < 100 ms

non‑triggering voltage [UW] Utn ‑ 10% Utn ‑ 10%

Residual voltage at rated current < 50 V < 50 V

making capacity [inSS] 50 ka 100 ka 50 ka 100 ka

Short time withstand current (0.1 s)

50 ka 100 ka 50 ka 100 ka

leakage current [il] n/a ≤ 50 ma

Breaking capacity at 600 V 900 a 900 a

Rated insulation voltage [Une] 3.6 kV 3.6 kV

impulse withstand voltage [Uni] 40 kV 40 kV

Power frequency withstand voltage [Ua] (50 Hz, 1 min)

18.5 kV 18.5 kV

Mechanical characteristics

overall dimensions (W x D x H) iP42: 800 x 650 x 1200 mmiP65: 835 x 825 x 1635 mm

iP42: 800 x 700 x 1500 mmiP65: 835 x 825 x 1635 mm

typical weight Up to 220 kg Up to 290 kg

Voltage limiting DeVice / Vguard4

VGuard-B

B A

1

2

3

4

CUSTOMER BENEFITS

D cost efficient.

D Simple installation through compact design.

D no commissioning required as the system is supplied ready for operation.

1 earthing contactor

2 SePcoS: Sécheron protection and control unit

3 Vm: Sécheron voltage measuring amplifier

4 miU: Sécheron current measuring amplifier

a to earth

B to negative bar

1

2

3 4

Voltage limiting DeVice / Vguard 5

VGuard-H

B A

1

2

3

4

5

67

8

CUSTOMER BENEFITS

D low maintenance due to application of thyristors.

D maximum protection for personnel and equipment thanks to short reaction time.

D Parameterization through the display.

D Simple installation through compact design.

D no commissioning required as the system is supplied ready for operation.

D especially adapted to application > 1 kV.

1 earthing contactor

2 SePcoS: Sécheron protection and control unit

3 Vm: Sécheron voltage measuring amplifier

4 miU: Sécheron current measuring amplifier

5 limiting resistor

6 anti‑parallel thyristors

7 thyristor command board

8 Surge arrester

a to earth

B to negative bar

1

2

3 4

5

6

7

8

Voltage limiting DeVice / Vguard6

OPERATION

PROTECTION PRINCIPLE

to ensure the safety of people and equipment, Sécheron’s Vguard ensures the following combined protection functions:

the short term protection aims at protecting people and equipment against dangerous accessible voltages that can arise in fault condition, such as the fall of a broken contact wire. Vguard‑H ensures this type‑F function which is required when the source of the impermissible voltage is the voltage on the contact line, when a fault occurs, and the risks are of electric shock by indirect contact as described in en 50122‑1 standard.

the long term protection provided by a VlD‑o corresponds to protection against impermissible touch voltages that may arise in normal operation due to the train traffic. a VlD‑o should be able to interrupt the current that flows in it, in order to minimize the risks from stray current. VlD‑os require a long term current capability.

the combination of thyristors and switching contactor allows Sécheron’s Vguard‑H to fulfill and cover the requirements of both protection function types: VlD‑F and VlD‑o.

/// VLD-O PROTECTION FUNCTION

in normal operation, the origin of the overvoltage is the train traffic and to the fact that permanent equipotential bonding should not be provided because of the risks from damage to assets by stray current, as described in en 50122‑2 standard. the Vguard monitors the voltage between the return circuit and earth and prevents that the voltage does not exceed the admissible values by short‑circuiting both potentials temporarily and opening automatically in order to minimize stray currents.

/// VLD-F PROTECTION FUNCTION *

in case of contact fault (i.e. fall of a broken contact wire) between a live part of the traction supply and a conductive earthed part in the overhead contact line zone (oclZ). the Vguard protects against an impermissible voltage by becoming conductive and causing a short‑circuit of the line which immediately triggers the release of the Dc high‑speed circuit breaker.

/// LIGHTNING PROTECTION OF INSTALLATION

it prevents equipment installed between negative and earth against overvoltage issued from lightning strikes / overvoltages.

0.01 0.1 1 10 100 10000

100

200

300

400

500

600

700

800

900

Time (s)

Voltage (V)

*Thyristor Contactor switch

EN 50122-1

SHORT TERM (VLD-F) LONG TERM (VLD-O)

* Only applicable for VGuard-H variant.

Voltage limiting DeVice / Vguard 7

OPTIONAL ASSOCIATION WITH SCMSStray current monitoring System (ScmS) is a straightforward and efficient method of stray current monitoring avoiding manual repetitive measurement and any interference with the stray current collecting system. the system measures continuously the rail‑to‑earth potential under operational conditions, complete with central analysis, visualization, signaling and archiving capacities.

already compatible with ScmS, the Vguard collects measurement along the line and transmits data via possible communication protocol.

– Voltage between the return circuit and the earth structure through a high accuracy sensor. – Potential current flowing in the Vguard through a high accuracy sensor. – Vguard status.

• TCP/IP: moDBUS‑tcP.

• Optional power distribution protocols: iec 60870‑5‑104 (‑5‑101), DnP 3.0, iec 61850.

• Flexibility in connectivity: copper cable (RS485, RJ45) or optical fiber.

VGuard

PLC

V

A

VGuard

PLC

V

A

VGuard

PLC

V

A

BUSS

TRAY

CU

RR

EN

TM

ON

ITO

RIN

G S

YS

TEM

Sécheron SA

Rue du Pré-Bouvier 251242 Satigny - Geneva

CH-Switzerland

www.secheron.com

Tel: +41 (0)22 739 41 11Fax: +41 (0)22 739 48 11substations@secheron.com

This document is not contractual and contains information corresponding to the level of technology at the date of printing. Sécheron reserves the right to modify and/or improve the product, whose characteristics are described in these documents, as required by new technology at any time. It is the purchaser’s responsibility to inform himself, no matter what the circumstances, of

the product’s maintenance conditions and requirements. Sécheron reserves all rights, especially those arising from our “General Delivery Conditions”.

Copyright© 2017 Sécheron SA

Sg825867Ben_D00‑09.17