At the beginning we had direct current (d.c.), the use of which would
have required a power station at each street corner. With the use of the
alternating current (a.c.) the problem of long buses and high of voltages was
solved. One had to face the problems of accessibility and not foreseeable
But a number of other factors limited the use of electric current.
Only a private power station could put things right, which the user could
attend and service. Over decades the good old Diesel served us well for all
types of emergency supply.
However, mains failure and mains return usually accompanied network
Modern electronics can do without such dinosaurs of electro-technology
and take shiftings and short-time interruptions (SI) amiss.
As a consequence, uninterrupted power supplies (USV or UPS) were
developed in order to supply energy for the consumers during a short malfunction.
The most substantial media were batteries and kinetic energy, which are
used up to highest power stages.
the data processing technology the philosophy of security was raised to a
religion and led to a great number of solutions, which were limited only by
short time storage: kinetic
long term storage: Diesel (modified)
short time storage: Battery
Long term storage: Diesel (modified)
converter, delta converter
redundance (secured A-supply)
Parallel to the network a system is constantly held ready, which adjusts
a malfunction immediately. A bypass becomes active with error or overload.
parallel connecting of several units and an oversizing (n+1) further security is
achieved. One UPS-unit can always break down.
static switch (SS) takes over the switching co-ordination.
(secured A-supply, secured or unsecured B-supply)
A second supply way is set up to the load, that
alternatively will be secured as an UPS branch.
At the load now a fast alternation switch can
choose between two supplies.
Interpretation: Load = Ĺ UPS1 + Ĺ UPS2
Each load with a static switch is secured.
system a redundance is designated for N-plants, which replaces a plant at a
time. Basis for the interpretation is a view of the
malfunction-probability and a view of economy. A redundant system for max. six
main facilitieses makes good technic and economic sense. The
continuing off-voltage stand-by mode of the redundant system is a disadvantage. Each load with a static switch is
system the redundance is integrated into each plant and must not be used. The height of the not usable load depends
on the number of parallel systems and is not changeable any longer.
2 facilities: 50% not usable
3 facilities: 33% not usable
4 facilities: 25% not usable
5 facilities: 20% not usable
reserve supply etc. (image 5)
of parallel UPS produces two UPS networks, the critical load is coupled over
STS. In a failure scenario the balance of loads is to be considered.
With this system the bypass is supported additionally by an UPS. Thus also load priorities are possible. (image 7)
meaning of A and B systems
about A and B systems, if two independent networks are available. For use a STS
( fast static transfer switch) is absolutely necessary. Up to the STS a double
installation is to be planned. Only in special cases there can be an A and B
system downstream of central STS. Here load variations are to be considered.
Without a registration of the load flux all systems are not operable in
meaning of a fast static transfer switch (STS) and a static switch (SS) :
Circuit speeds of circuit-breakers are usually too long and cause
short-time interruption (SI), in particular if one switches over to another
For that fast static switches (STS) were developed, which make the
shifting between networks.
Both networks (A and B) should be almost in phase, in order to avoid
current peaks during the shifting.
Thus STS is absolutely necessary with the supply with 2 networks.
the A- and B-network must be interpreted for the full load of the running
thus: LOAD = A = B.
switches (SS) are components of an UPS and take over the function of automatic
bypasses. A hand bypass is additionally necessary.
load-referred STS with A- and B-adapter (shown in image 3)
(separated full installation for A and B close to STS and load)
Version 2: central
STS for 100% A and 100% B and 100% load (shown in image 4 and 5)
For A + B at the STS a hand bypass must be available.
adapters with A and B are possible, but not necessary. Here the load balance is
to be considered.
double central STS for 50% A and 50% B and 50% load, a load-referred (smaller)
STS is absolutely necessary, that enabled the complete shifting from A to B or
shown in image 8)
Without a load-referred (small) STS the system is useless and involves a certain risk.
The combination of those versions is a question of philosophy and depends
on the amount of the investment. An expansion of level is always possible (except
version e), but not an exchange of versions.
Donít mix different versions of redundant systems.
The general non-critical load is to be considered separately.
The planner/advisor is responsible for the operation of the facilities
from mains supply to load considering the following items:
-- traffic routes, weights
-- stages of development
-- availability of space according to the importance of the facilities
-- conditions given through the construction certificate
-- network configurations
-- harmonic wave measurement and controlling
-- fault signals
-- emergency shut-downs
-- load management/load lines
-- letting conditions
-- load test in the network
-- overvoltage protection/lightning protection
-- short circuit and selectivity
-- emission of noise and waste gas
-- refueling systems
-- facility cooling
-- escape and emergency routes
-- security management