I wished to transfer BTC, and i found that for sending 0.0020 I have to pay 0.0030 as transaction fee
¿how it is possible?
If any of the outputs of a transaction are less than 0.01 BTC, then the reference client Bitcoin-Qt will force you to pay a 0.0005 BTC fee.
If your wallet consists of receiving dozens of really tiny transactions (such as from "Free Bitcoin" sites or playing Satoshi Dice), then your transaction will get very large (in terms of bytes) and the Bitcoin-Qt wallet will force you to pay a fee of
0.0005 BTC per kilobyte.
If your total balance in your wallet is
more than 0.01 BTC and you (or someone you trust) has access to a larger number of bitcoins, it can be possible to consolidate all those tiny "dust" transactions into a single larger transaction that can be spent without a fee.
If your total balance is
less than 0.01 BTC, and you (or someone you trust) has access to a larger number of bitcoins, it can be possible to consolidate all those tiny "dust" transactions into a single larger transaction that can be spent with a single 0.0005 BTC fee instead of 0.0005BTC per kilobyte.