|
|
 |
Induction generator never
trips due to steam load fluctuations unlike
an alternator. The power generator will vary
in proportion to the steam flow rate. If steam
flow rates falls below a critical value (say<20%
of designed value) the IG will go into motoring
mode.
|
|
Fluctuations in inlet steam pressure ? |
|
Induction
generators continue to operate in spite of large
fluctuations in inlet pressure unlike an alternator.
The power generator will vary in proportion
to the pressure at inlet. If it falls below
as critical value(say<50% of designed value),the
IG will go into motoring mode. |
|
Paralleling with a DG
set ?
|
|
It is
possible as long as DG governor is stable and
DG power rating is atleast 30% greater than
IG. |
|
|
| |
| Turbine module |
35% |
| Gear box module |
25% |
| Induction Generator |
20% |
| Controls and instrumentation |
10% |
| Mounting skid and miscellaneous |
10% |
|
|
How to control power factor
?
|
|
Power factor will be corrected
at site depending upon the client's existing capacitor
bank and existing power factor. We will provide
banks of 10KVAR and keep adding as necessary at
the time of installation to bring the P>F better
than 0.85 lag. |
|
Is water quality a problem
? |
|
For saturated steam applications
no particular care is needed as all the dissolved
salts will be in the boiler. If it is good for
the boiler, it will be acceptable to the turbine
also. Further since we are using hardened stainless
steel for the turbine, effects of erosion and
corrosion are minimal. In case of super heated
steam, silica content needs to be monitored closely
(less than 1ppm). |
|
Life of turbine ? |
|
15 Years since we are using
hardened stainless steel for the turbine rotor |
|
Time between overhauls ? |
|
It is estimated to be 3 years
or more, with an annual inspection. |
|
What about spares and maintenance
? |
|
We recommended the following. |
| |
| Bearings and seals |
Annual inspection and change
if necessary |
| Lube oil change |
Every three years |
|
| |
Some fast moving and low cost
spares like oil filters, gaskets, fuses, relays,
etc. will be handy and the same will be advised
during installation. |
| |
It is advisable to order
for one set of bearings and seals along with the
turbine. |
|
Life on saturated steam
? |
|
It is expected to be 15 years
since we are using hardened stainless steel for
the turbine rotor. However adequate care is to
be taken to ensure that only dry steam enters
the turbine and this can be simply accomplished
by installing an efficient moisture saperator
(with thermodynamic trap) and a Y-strainer in
the inlet line to the turbine. This is not included
in standard scope of supply. |
|
Super cooled vapor. |
|
The steam existing the nozzle
will be in a super cooled state and the passage
through the turbine takes less than a milli-second.
It takes about 1 to 2 secs, for condensation to
occur and all the condensation will occur down
stream of turbine, hence not harmful to the turbine.
In addition, since it is a hardened stainless
steel blisk, there is no erosion on saturated
steam. |
|
How an induction Generator
works ? |
|
Whenever an induction motor
is run higher than its synchronous speed by the
help of a prime mover it starts generating power
instead of absorbing power. All induction machines
always operate at a lagging power factor (i.e,
the current vector lags the voltage vector and
the cosine of the angle of the lag is defined
as the power factor).The power factor depends
on the slip which is a function of the loading
of the motor. The lag angle will be 90 deg when
the machine runs at zero slip, that is at synchronous
speed and this is known as quadrature. At quadrature,
it will neither absorb nor generate power. If
with the help of a prime mover such as the turbine,
the speed is increased beyond synchronous, the
lag angle increases beyond 90 degrees and the
power factor becomes negative. Therefore the power,
i.e. VI CosØ will be negative which means
the machine is generating power. The power factor
is adjusted by adding the required KVAR capacitor
bank.
Since the excitation of the IG is from the grid,
it does not require any governing. Grid acts as
the governor. Also it does not calls for synchronizing
as it automatically locks itself to the grid. |
|
Safety interlocks ? |
|
ECT is wired to shut down
safely in the any of the following undesirable
operating conditions. |
| |
 |
High lube oil temp. |
|
Low lube oil pressure. |
|
Low air pressure (to valve actuator). |
|
Over speed (which is unlikely). |
|
Over voltage. |
|
High winding temp. |
|
Earth leakage. |
|
Over load. |
|
|
The trip will be annunciated
and a hooter will come `ON` and one has to accept
and reset before restarting. |
|
In addition an emergency trip
(Mushroom button switch) is also provided. |
|
Advantages of high speed
? |
|
ECT is a high speed turbine.
Following are the merits. |
| |
|
For a given enthalpy drop,
the turbine diameter is small. |
|
Hence for a particular mass flow, the
arc of steam admission will be larger |
|
This results in lower losses caused by
partial admission. |
|
This enhances the adiabatic efficiency
of the turbine. |
|
Means higher power for the same steam
parameters. |
|
|
Alternator Vs Induction generator
? |
|
Induction generator has the
following advantages. |
| |
|
IG does not require a governor,
the associated governing valve and actuator |
|
No synchronizing. |
|
No load management is required. No load
shedding under any steam demand condition. |
|
Can accept wide fluctuations in steam
flow and inlet pressure. |
|
Makes most effective use of process steam
flow, maximizes power generation. |
|
|
Can ECT take a mechanical
drive? |
|
It is possible to drive but
would require a governor to control the speed
of the driven equipment. We will quote on a case
by case basis. |
|
Reverse power relay ? |
|
Induction generator does
not need a reverse power relay. Since the chances
of going into motoring mode are so infrequent
and as grid power is essential during starting,
reverse power relay is not recommended. If the
client insists, the same can be implemented at
extra cost. Please be reminded that this will
have to be bypassed during starting and operational
manpower cost will go up. IG does not require
any attention and it is a ` fit and forget ` system. |
| |
Highlights of ECT Turbines.
|
| |
| |
High speed - high efficiency
turbine, 60% of isentropic enthalpy drop
to electrical power. |
| |
Customized design, maximum efficiency
for a given steam conditions. |
| |
Low noise, high efficiency gearbox. |
| |
Pressurized lube oil circulation system. |
| |
Hardened stainless steel turbine and
SS casting for all steam wetted parts. Hence
frequent starts possible. |
| |
Inherent design safety to ensure that
the turbine can never cause any ballistic
damage due to over-speeding. This is accomplished
by |
| |
|
Proper choice of turbine
material of high strength and elongation |
|
Maintaining very tight clearance
between turbine tip and shroud so
that the turbine can at worst rub
the shroud and come to a screeching
halt and cause no damage to the personnel
if present near the turbine. |
|
SS shroud of the turbine act as
a containment enclosure which has
a very high elongation of 70% before
rupture |
|
| |
Designed to handle saturated steam. |
| |
Life of turbine virtually unlimited. |
| |
Zero leakage sealing system, preventing
steam leakage losses of nearly 3 to 4 lakh
rupees annually. |
| |
Lightweight, skid mounted with AVM`s,
no foundation necessary, no cost to customer
on civil works, faster installation time. |
| |
High power to weight ratio. |
| |
Use of induction generator eliminates
governor. It automatically synchronizes
with the grid and no load management is
called for. It allows maximum exploitation
of steam potential available at a client’s
works. |
| |
“Fail safe” interlocks to
ensure safety of equipment. |
| |
Can accept pressure fluctuations at inlet
and varying steam flows with out tripping. |
| |
Total service support and fast response
to service calls. |
|
