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FIELD OF INVENTION
The invention relates to monitoring and controlling of electrostatic precipitators
used for air pollution control. More particularly, the invention relates to an
improved system for interfacing signals between High Voltage Rectifiers and
Electronic controllers in electrostatic precipitators by adapting open standard
wireless protocol by replacing signal cables running between the high voltage
Rectifiers and electronic controllers.
BACKGROUND OF INVENTION
Electrostatic precipitation is one of the most effective ways to control air
pollution generated by industrial emissions. This technique, which has proven
highly effective in controlling air pollution, has been used for removal of
undesirable matter from a gas stream by electrostatic precipitation. Electrostatic
precipitator (hereafter referred to as ESP) is an air pollution control device
designed to electrically charge and collect particulates generated from industrial
processes such as those occurring in power plants, cement plants, pulp and
paper mills and utilities etc. The electrically charged particles are attracted
towards electrode plates, viz., discharge electrode and collection plate. ESP is
divided into a plurality of fields depending on the dust load. A field is
considered healthy as long as it is charged with sufficient voltage and current
between its discharge and collection plate. During continuous operation of an
electrostatic precipitator, the dust from collector plates & discharge electrodes
must be periodically removed for further conveying of the collected dust.

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Typically, energizing ESP field requires a very high voltage to the tune of 40 to
90KV DC to be generated from the available AC sources. This involves stepping
up of AC voltage and rectifying to produce such a very high voltage. Also, the
generated high voltage needs to be maintained and controlled during the
operation of the ESP field. This is generally being achieved by High Voltage
Rectifier with electronic controllers (EC-HVR). The ESP fields are arranged in
pass-wise along the distribution of gas flow direction. For a typical larger ESP,
there will be around 8 pass's and each pass will have around 8 fields depending
on the size of ESP totaling 64 EC-HVRs. Typically, the Electronic Controller (EC)
and High Voltage Rectifier (HVR) are placed at different locations in a plant due
to operating requirements.
In the prior art, mechanism exists to integrate EC & HVR through signal cables
such that signals like secondary voltage, secondary current and other sensor
inputs are directly connected to the EC through individual signal cables. For a
typical power plant, the amount of cables required for such signal sensing runs
into kilometers thereby resulting in increased installation cost. Also, time taken to
commission all these cables is very high.
Each ESP field is controlled by an individual ESP controller, thereby effectively
controlling the EC-HVR set. These ESP field controllers, being more in number for
a typical plant, are networked through communication interface for ease of
operation. Also, there exist methods to control and monitor all these ESP field
controllers through separate operator terminals or a centralized controller
(OTCC) connected to the same communication network directly or connected
through gateway electronics. All signals and alarm information of the HVR are .

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communicated to the OTCC via the ESP controller, which leads to a substantial
delay in the presentation of critical activity to the OTCC.
The subject invention seeks to overcome drawbacks of using wires between HVR
and EC and improve the system management using wireless means.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved system for
interfacing signals between High Voltage Rectifiers and Electronic controllers in
electrostatic precipitators by adapting open standard wireless protocol by
replacing signal cables running between the high voltage Rectifiers and electronic
controllers which is capable to monitor analog and digital parameters of the ESP
for example analog signals like electrical voltage and electrical current and digital
signals like alarm signals.
A still another object of the invention is to propose an improved system for
interfacing signals between High Voltage Rectifiers and Electronic controllers in
electrostatic precipitators by adapting open standard wireless protocol by
replacing signal cables running between the high voltage Rectifiers and electronic
controllers which is enabled to monitor all signals from HVR to EC by wireless
means to reduce usage of cables for signal monitoring and control.

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Yet another object of the invention is to propose an improved system for
interfacing signals between High Voltage Rectifiers and Electronic controllers in
electrostatic precipitators by adapting open standard wireless protocol by
replacing signal cables running between the high voltage Rectifiers and electronic
controllers which is provided with wireless interface based on open standard
interface with the EC, HVR and OTCC.
A further object of the invention is to propose an improved system for interfacing
signals between High Voltage Rectifiers and Electronic controllers in electrostatic
precipitators by adapting open standard wireless protocol by replacing signal
cables running between the high voltage Rectifiers and electronic controllers
which improves reliability and availability of communication using peer-to-peer
communication, multi-master communication and periodical communication from
the ESP controllers.
SUMMARY OF THE INVENTION
According to the invention, the microprocessor based system comprises three
major components viz., HVR Electronics (HVR-E), EC Electronics(EC-E) and
Zigbee wireless interface (ZWI). HVR-E is developed using a 32-bit processor
with associated peripheral components for analog and digital signal scanning. It
also has Radio Frequency(RF) end with protocol stack for zigbee wireless
interface (ZWI). Similarly, the EC-E is designed with suitable processor with
associated peripheral components for RF end for ZWI.

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HVR-E detects alarm signals immediately upon their occurrence and transport
them to respective EC-E over zigbee network in non-beacon mode. The topology
of the implemented configuration is mesh type. The mesh network maximizes
the availability of network even there is break in network. The communication
packets will reach the destination through alternate path during such failures.
The received communication packets at respective EC-E will be processed
immediately and necessary action is taken. Similarly, secondary voltage signals
viz., average KV, peak KV and valley KV sensed at HVR-E are also transported to
respective EC-E through zigbee network in beacon mode. The configuration of
zigbee network is such that all channels in 2.4GHz range are evenly distributed
among HVR-E & EC-E pairs so that none of the frequency channels are loaded
heavily. The secondary signals are transmitted to respective EC-E during every
zero-crossing of AC waveform.
The transmitted signal over zigbee network can also be received by OTCC if
enabled suitably. This will lessen the load on EC-E and also speed-up the
reception of field signals at OTCC.
The invention will now be described in detail with reference to the accompanying
drawings.

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BREIF DESCRIPTION OF ACCOMPANYING DRAWINGS
FIG.l is a block diagram illustrating a co-ordinator device in a microprocessor-
based control system according to the invention.
FIG.2 is a block diagram illustrating a HVR-E controller device in a
microprocessor-based control system according to the invention.
FIG.3 is a block diagram illustrating a EC-E controller device in a microprocessor-
based control system according to the invention.
FIG.4. a network diagram between the EC-E & HVR-E of the invention.
FIG.5 is a block diagram illustrating a communication bus scheme in the system
according to the invention.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the block diagram shown in fig.l, the coordinator hardware is shown. A
microcontroller (1) is connected to a RF communiation interface (2) through a
system bus. The software modules and zigbee stack is loaded into the
microcontroller(l) and configured as zigbee coordinator. The coordinator (11) is
the only system capable of starting and stopping zigbee network and adding any

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new node to the network.
In the block diagram shown in fig.2, the HVR-E(13) hardware is shown. HVR-
E(13) contains a microcontroller^) connected to analog input(4), digital input(5)
and RF communication interfaced). They are connected through system bus.
The HVR-E(13) senses all required signal through the inputs and sends them to
respective EC-E(12) over zigbee network
In the block diagram shown in fig.3, the EC-E(12) hardware is shown. EC-E(12)
contains a microcontroller^) connected to input(8), output(9) and RF
communication interface(lO). They are connected through the system bus. The
EC-E(12) receives all required signals from respective HVR-E(13) over zigbee
network and does controlling activity according over its outputs(9).
In the fig.4: Network diagram for interfacing between the HVR-E(13) and EC-
EC^) over zigbee is shown.
In the fig.5: Network diagram for interfacing to third party system (14) & OTCC
(15) is shown. They are all connected in mesh network topology.
According to the invention, the wireless protocol used is Zigbee -an open
standard based wireless protocol. The zigbee network topology used for this
application is a mesh network. The zigbee is operating in both beacon and non-
beacon mode for communication between the HVR and EC. As described
hereinabove, the zigbee network has a coordinator (11), which manages the
entire zigbee network. The coordinator (11) is a separate electronic system
different from the HVR-E (13) and EC-E(12). The coordinator (11) is normally
placed in ESP control room. It starts and manages the zigbee network. Each HVR

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is having its own electronic system, HVR-E(13), for sensing digital inputs and
analog inputs and RF interface for communication over zigbee network. Each
HVR-E (13) is supported by software modules, and HVR-E(13) is configured as a
full function device (FFD). The HVR-E(13) has a microprocessor, input/output
peripheral, RF interface and software modules & stacks. It senses all HVR signals
including average KV, maximum instantaneous KV, minimum instantaneous KV &
critical and non-critical Alarms and transmit the sensed signals to respective EC-E
(12) over zigbee network using beacon and non-beacon mode after joining the
network as FFD. Each EC is having its own electronic system, EC-E (12), for
controlling inputs and outputs and RF interface for communication over zigbee
network. Each EC-E(12) is coupled with suitable software modules and the, EC-E
(12) is configured as a FFD (full function device). The EC-E(12) has a
microprocessor, input/output peripherals, RF interface electronics and software
modules & stacks. It reads signal information from the respective HVR-E(13)
over zigbee network for control action after joining the zigbee network as FFD.
An operator terminal and centralized computer (OTCC) (15) are provided with
zigbee interface for directly monitoring the sensors and commanding the EC-E
(12). The OTCCs (15) are linked to the zigbee network as FFDs and continuously
monitor the system without need to connect to sensors and controllers
physically. The OTCC(15) is provided with zigbee interface and communicates
with the sensors and electronic controllers through the zigbee wireless network.
The entire system can be monitored and controlled by any third party system
(14) directly if the coordinator (11) accepts the third party system as one of its
sub-system and if the third party system (14) has required zigbee interface.

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WE CLAIM
1. An improved system for interfacing signals between high voltage rectifiers
and electronic controllers in electrostatic precipitators (ESP) by adapting
open standard wireless protocol, comprising:
- a network coordinator (11) in particular for zigbee network,
comprising a microcontroller (1) connected to a RF-communication
interface (2) via the system bus, the microcontroller (1) being
loaded with software module including zigbee stack, the
coordinator (11) managing the network and capable of adding any
new node to the network;
- a plurality of high voltage rectifier controllers (HVR-E(13) for
sensing digital inputs and analog inputs and comprising a
microprocessor, RF-interfacing for communicating over the zigbee
network, and software module and stacks, the HVR-E (13)
transmitting the sensed signals to respective electronic controllers
(EC-E12) over the network; and
- a plurality of electronic controllers (EC-E(12)) for the ESP, each
having microprocessor, RF interface, and software modules for
receiving signals from the HVR-E (13) over the network and
accordingly effect control action of the ESP.

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2. The system as claimed in claim 1, comprising an operator terminal
including a centralized computer device (15) provided with zigbee
interface for directly monitoring the sensors of the ESP and transmitting
command to the EC-E(12).
3. The system as claimed in claim 1 or 2, comprising a third party system
(14) for directly monitoring and controlling the ESP under the compatibility
with the network coordinator (11), the third party system (14) being
provided with zigbee interface.
4. An improved system for interfacing signals between high voltage rectifiers
and electronic controllers in electrostatic precipitators (ESP) by adapting
open standard wireless protocol, as substantially described herein with
reference to the accompanying drawings.

This invention relates to an improved system for interfacing signals between high
voltage rectifiers and electronic controllers in electrostatic precipitators (ESP) by
adapting open standard wireless protocol, comprising; a network coordinator
(11) in particular for zigbee network, comprising a microcontroller (1) connected
to a RF-communication interface (2) via the system bus, the microcontroller (1)
being loaded with software module including zigbee stack, the coordinator (11)
managing the network and capable of adding any new node to the network; a
plurality of high voltage rectifier controllers (HVR-E(13) for sensing digital inputs
and analog inputs and comprising a microprocessor, RF-interfacing for
communicating over the zigbee network, and software module and stacks, the
HVR-E (13) transmitting the sensed signals to respective electronic controllers
(EC-E12) over the network; and a plurality of electronic controllers (EC-E(12)) for
the ESP, each having microprocessor, RF interface, and software modules for
receiving signals from the HVR-E (13) over the network and accordingly effect
control action of the ESP.