FGD-2 Connections

Connectors with screw-down compression terminals are used for all FGD-2

connections. The connectors, and the headers that they plug into, have a

dovetailed edge that ensures proper connector orientation. Similar-sized

connectors and headers are uniquely keyed to ensure that a connector

mates only with the correct header to prevent damage to the FGD-2.

However, care must still be taken to ensure that the proper connector is

inserted into the appropriate header. Connector screw terminals accept a

maximum wire size of 8 AWG. The maximum screw torque is 7.1 in-lb or

0.8 N•m. Figure 2 illustrates typical FGD-2 connections.

The FGD-2 was designed to be connected between F+ and ground, but

it is also compatible with applications where only F– is available.

Figure 3 illustrates this alternate connection option.

Overview

The DECS-250N digital excitation control system offers high performance, high

flexibility, and extreme reliability for brushless excited AC synchronous generators.

The DECS-250N utilizes a 20-amp six-thyristor negative forcing output, providing

exceptional system transient response. Multiple communication options and an

optional integrated power system stabilizer make the DECS-250N a complete system

solution in a reliable and cost effective package.

Benefits

• The Offline Simulator, provided in BESTlogic™Plus, helps test and

troubleshoot logic without the need for expensive hardware.

• Reduce setup time with Basler’s intuitive BESTCOMSPlus®

software that simplifies complex setup with simple drag-and-drop

programmable logic, visual real-time strip chart capabilities, and

cutting edge auto PID selection capabilities.

• The revolutionary auto tuning function automatically establishes

optimum PID and gain settings, taking the guesswork out of

system setup, reducing commissioning time and cost while

maximizing overall system performance.

• A powerful 20-amp rectifier bridge provides high positive and

negative field forcing for exceptional system response. The

negative field-forcing capabilities make it well suited to be paired

with the optional Power System Stabilizer.

• Grid code settings provide compatibility with grid code compliant

systems.

• Easy user-configurable settings for synchronous motor or

generator modes of operation.

SAFETY

As with all electrical equipment, appropriate safety measures must be taken

when dealing with excitation equipment. High voltage is present within the

excitation cubicles; their magnitudes depend upon the particular system.

Opening the sources (e.g., disconnecting device 41) does not completely

disconnect the high voltages.

As long as the machine is still physically connected to the system, there is

a possibility that a safety hazard exists.

Every precaution must be taken when working at the excitation control

switchgear to ensure that all high voltages are isolated and avoided by

test personnel. In addition to the machine terminal voltage (460 Vac or

greater) at the excitation transformer, there may be other sources of power

entering the cubicles, such as 125/250 Vdc and/or 120/240 Vac used to

feed certain devices. A good rule to follow is to assume that all connections

are live and dangerous until proven otherwise and to avoid all body contact

with any of these voltages.

DXCB-2 Models

Three versions of the DXCB-2 module are available. Part number 9500900100

is rated for up to 600 Vdc nominal field voltage and can conduct up to

2.000 Adc for one second. Part number 9500900101 is rated for up to 1.000

Vdc nominal field voltage and can conduct up to 5.000 Adc for one second.

Part number 9500900102 has identical ratings to part number 9500900101

but has a higher range of jumper-selectable trip voltage values.

Reference Table 3 for jumper-selectable trip voltages for each model.

INSTALLATION

The DXCB-2 is typically preinstalled in the excitation control system. If

replacement is necessary, carefully label and document each of the

connections to the DXCB-2 in order to properly reconnect the new module.

The DXCB 2 must be monitored and adjusted to fit the specific application

at initial startup, whether it is a new unit or a replacement.

INTRODUCTION

The DXCB-2 De-Excitation/Crowbar Module protects the generator field

and exciter circuits by providing a low impedance path for currents that

would otherwise cause excessively high transient voltage or damaging

arcs. A DXCB-2 module can be operated in one of two modes: de-

excitation (DX) or crowbar (CB).

In DX mode, the DXCB-2 module provides a path for the generator field

current when its field breaker is opening or when the normal path is not

available.

In CB mode, the DXCB-2 module provides a low-resistance path for large

positive voltages across the generator field and exciter bridge. Generator

pole-slip is one source of high voltage.

The enclosure of the DXCB-2 offers electric shock protection from incidental

contact. An identical footprint and functional compatibility make for simple

replacement of a DXCB with a DXCB-2.

Installation

The FGD-2 is typically preinstalled in an excitation control system.

If replacement is necessary, carefully label and document each of the

connections to the FGD-2 in order to properly reconnect the new module.

FGD-2 connectors and indicators are illustrated in Figure 1. Locator

letters in Figure 1 correspond to the lettered descriptions in Table 1.

When a replacement FGD-2 is installed in a DECS-2100 or ECS2100

system, the system calibration values may need to be updated.

Retrofitting an FGD

Although the FGD-2 is smaller in size than the FGD, it may still be mounted

in place of an FGD using only four of the six existing mounting holes.

Either the upper four or the lower four mounting holes may be used.

BE1-FLEX

The FGD-2 output can be connected to any analog input of the BE1-FLEX.

Field ground protection settings can be configured in BESTCOMSPlus.

Ground Detection Source

The ground detection source supplies approximately –60 Vdc to the positive

side of a machine field and measures the level of leakage current to ground.

The positive side of the field bus is held negative with respect to ground.

Introduction

The FGD-2 Field Ground Detector Module is a transducer that continuously

monitors the resistance of the field circuit of a synchronous machine with

respect to ground. It applies a fixed voltage with respect to ground which

causes a small leakage current to flow. The FGD-2 provides a low voltage

output signal proportional to the leakage current.

The voltage output is measured by a compatible product and used for

field ground protection. Two versions of the FGD-2 are available. A low-

voltage version, rated for 800 Vdc maximum generator field voltage, is

provided for brush or brushless exciter systems. A high-voltage version,

rated for 1.750 Vdc generator field voltage, is provided for static exciter

systems.

The metal enclosure of the FGD-2 offers electric shock protection from

incidental contact. A compatible footprint and identical functionality

make for simple replacement of a Field Ground Detector (FGD) with the

FGD-2.

BESTdata is a powerful tool that enables users to reverse time and analyze

previously recorded event data in high detail.

This level of analysis is essential for identifying the root cause of system

events-especially when basic magnitude measurements alone are insufficient.

— Product Features & Benefits

• View and Analyze COMTRADE records: BESTdata is based upon and

able to work with COMTRADE standardized records.

The software can not only open the records, but also perform complex math

and other functions to further process the data.

Pre-canned visuals allow for quick insight to analog, digital data as well as

phasors, RMS, peak and other commonly used variables.

• Virtual Channels: Digital equipment only measures voltage and current.

All other quantities are calculations of these two pieces. Similarly, COMTRADE

records typically only show voltage and current as separate channels.

Virtual channels are utilized to calculate most any other algorithm that we use

in Power Systems such as Impedance, Power, Differential Current and a wide

variety of other math functions.

Trajectory and Phasor graphics are available to view event progression through

the recordings. Trajectory graphs can be configured for not only voltage and

current, but also calculated quantities such as Impedance, Power and

Symmetrical Component calculations.

Modern digital devices offer a wide range of configurable settings to meet

diverse application needs. With so many parameters and functions available,

it is essential to have a user-focused interface.

BESTCOMSPlus® delivers that, helping users visualize device configurations,

and confidently manage system interactions for commissioning, operation,

and diagnostics.

BESTCOMSPlus® is used to set and monitor the BE1-FLEX, BE1-700V, BE1-11.

DECS-150. DECS-250. DECS-250E, DECS-250N, DECS-450. DGC-2020.

DGC-2020ES, and DGC-2020HD.

— Product Features & Benefits

• Logic:

Graphical Logic with Offline Simulation and Real Time Status: Graphical drag

and drop logic is simple to implement and greatly reduces the possibility of

errors. Logic Simulation and Real Time Logic Status further add visibility to see

exactly how a device configured and what it is doing.

• Metering & Commissioning Tools:

Real Time Analysis and Recording, Step & Frequency Response injection tools,

Control Panels, Phasor Diagrams, Real Time Logic Status, Extensive Metering

and Status capabilities all contribute to improving commissioning time and

confidence. These tools are useful for commissioning, troubleshooting, and

NERC compliance testing.

• Settings:

Graphical settings and logic provide a visual check of the settings to reduce

the possibility of inadvertent settings. Settings are logically organized in a

tree menu, making finding the setting of interest super easy.