Ingenieur Vol. 75 ingenieur July 2018-FA | Page 19

to further increase the contribution of RE to the
power sector.
LSS, NEM and Selfco limited to PV technology
and Virtual Generators not allowed
At present, all the above mechanisms are limited
to PV on the customer’s own premises. Non-PV
technologies are on a case by case basis, and so far,
there have been no success stories although many
developers of small industrial estates and housing
estates are interested to have a RE contribution,
both for commercial, as well as Corporate Social
Responsibility (CSR) reasons. This is because there is
no clear mechanism to allow for non-PV generation.
Apart from that, virtual generators should also be
allowed, i.e. the RE generation may be off-site but
allowed to sell to a particular customer by using the
utility’s network for a fee.
Co-generation and New Enhanced Dispatch
Arrangement
Most consumers do not go for co-generation
(co-gen) due to the prohibitive rates charged by
the utility. Recently, the EC launched the New
Enhanced Dispatch Arrangement (NEDA), aimed
primarily at Independent Power Producers (IPPs)
with expired PPAs and those with existing PPAs but
willing to sell at a lower cost than the PPA price.
Cogens are also allowed to participate in NEDA
but need to follow the same mechanism as the
big boys, i.e. day ahead dispatch schedules with
spot prices offered by the Single Buyer. Cogens
using waste heat and other forms of renewable
energy should be offered more flexibility in terms
of dispatch schedules and spot prices.
TECHNICAL ISSUES AFFECTING
INCREASE IN RE GENERATION
The most important issues affecting the increase
of RE generation, whether under FIT, LSS, NEM
or other schemes, are the technical issues put
forward by the utility to limit or stop RE generation.
Some of the major issues are listed below.
• Lack of Load and Voltage Rise
This issue normally affects the biogas, small
hydro or other RE plants connected at a remote
end of the distribution network where the load is
very small. This usually results in an increase in
voltage when power is injected at this remote end,
sometimes beyond the +5 % allowed for medium
voltage systems. The utility has allowed operations
at leading power factor (where the current leads
the voltage) or use of a reactor (basically an
inductive device) to absorb reactive power from
the network and bring the voltage down. However,
this arrangement is counter-productive for the
utility as reactive power is produced by other
generators and there are technical losses in the
system due to the absorption of reactive power
by the generator. Conductor sizes may need to
be increased due to the reverse flow of reactive
power. Based on technical and commercial
considerations, the utility should not allow this
kind o f arrangement.
However, the utility should allow for power
flow from one voltage level to a higher voltage
level, as long as the voltage rise is within limits.
For example, from low voltage (LV) to 11 kV, and
also to higher voltages, including 132 kV. In many
jurisdictions in Europe, the Indian sub-continent
and China, there is no restriction in allowing power
to flow upstream. The objection by the utility is
normally based on two considerations: losses
in the step-down transformers and protection
issues. The losses are a non-issue since whatever
losses incurred in the step-down transformer
are made up by reduction of losses in the overall
distribution network. Detailed discussions with
protection experts in both Distribution and
Transmission networks have also revealed that
in normal circumstances, there are no protection
issues; whatever issues may arise can easily be
resolved through technical solutions which the RE
developer would be only too glad to pay for.
• High Fault Current at Main Utility Substation
(Transmission/Distribution Interface)
This is the bane of many RE developers. Even
in urban and heavily populated areas, many
potential RE generators have been stopped
due to this reason, even those proposing pure
self-consumption schemes. The 11 kV vacuum
circuit breakers (VCBs) at the main substations
are normally rated at 20 kA. When there is high
generation from IPPs in the vicinity the fault current
at the Main Substation increases. A number of
substations with a 132/11 kV interface already
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